diff --git a/.chronus/changes/support-nested-api-version-config-2026-08-20.md b/.chronus/changes/support-nested-api-version-config-2026-08-20.md
new file mode 100644
index 0000000000..0156b6bebb
--- /dev/null
+++ b/.chronus/changes/support-nested-api-version-config-2026-08-20.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+Support nested service namespaces in per-service `api-version` configuration.
diff --git a/packages/typespec-client-generator-core/README.md b/packages/typespec-client-generator-core/README.md
index c1d7a73fa0..1c12fd6894 100644
--- a/packages/typespec-client-generator-core/README.md
+++ b/packages/typespec-client-generator-core/README.md
@@ -64,7 +64,7 @@ When set to `true`, the emitter will generate convenience methods for each servi
 
 **Type:** `string | object`
 
-Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.
+Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.
 
 **Options:**
 
diff --git a/packages/typespec-client-generator-core/src/context.ts b/packages/typespec-client-generator-core/src/context.ts
index a2b516f6ca..ef20350850 100644
--- a/packages/typespec-client-generator-core/src/context.ts
+++ b/packages/typespec-client-generator-core/src/context.ts
@@ -231,7 +231,7 @@ export async function createSdkContext<
     generateProtocolMethods: generateProtocolMethods,
     generateConvenienceMethods: generateConvenienceMethods,
     namespaceFlag: context.options["namespace"],
-    apiVersion: context.options["api-version"],
+    apiVersion: context.options["api-version"] as TCGCContext["apiVersion"],
     license: context.options["license"],
     decoratorsAllowList: [...defaultDecoratorsAllowList, ...(options?.additionalDecorators ?? [])],
     previewStringRegex: options?.versioning?.previewStringRegex || tcgcContext.previewStringRegex,
diff --git a/packages/typespec-client-generator-core/src/interfaces.ts b/packages/typespec-client-generator-core/src/interfaces.ts
index a8678efbb3..632401db3f 100644
--- a/packages/typespec-client-generator-core/src/interfaces.ts
+++ b/packages/typespec-client-generator-core/src/interfaces.ts
@@ -35,6 +35,12 @@ import type { ContextNode } from "./internal-utils.js";
 
 type SourceKind = "RequestParameter" | "RequestBody" | "ResponseBody";
 
+export type ApiVersionConfig = string | ApiVersionServiceMap;
+
+export interface ApiVersionServiceMap {
+  [namespaceSegment: string]: string | ApiVersionServiceMap;
+}
+
 export interface TCGCContext {
   program: Program;
   diagnostics: readonly Diagnostic[];
diff --git a/packages/typespec-client-generator-core/src/internal-utils.ts b/packages/typespec-client-generator-core/src/internal-utils.ts
index 064c49201a..dc9d36e2e0 100644
--- a/packages/typespec-client-generator-core/src/internal-utils.ts
+++ b/packages/typespec-client-generator-core/src/internal-utils.ts
@@ -70,6 +70,8 @@ import {
   getParamAlias,
 } from "./decorators.js";
 import type {
+  ApiVersionConfig,
+  ApiVersionServiceMap,
   DecoratorInfo,
   ExternalTypeInfo,
   SdkBuiltInType,
@@ -98,7 +100,7 @@ export interface TCGCEmitterOptions extends BrandedSdkEmitterOptionsInterface {
 export interface UnbrandedSdkEmitterOptionsInterface {
   "generate-protocol-methods"?: boolean;
   "generate-convenience-methods"?: boolean;
-  "api-version"?: string | Record<string, string>;
+  "api-version"?: ApiVersionConfig;
   license?: {
     name: string;
     company?: string;
@@ -1016,9 +1018,10 @@ export function handleVersioningMutationForGlobalNamespace(context: TCGCContext)
  * - When the option is a string: `latest` is a global keyword; any other string
  *   (a specific version or `all`) applies only to the single service case and is
  *   ignored for multi-service packages.
- * - When the option is a record, the version is looked up by the service
- *   namespace's full name. Services that are not listed return `undefined`
- *   (meaning "use the latest version").
+ * - When the option is a map, the version is looked up first by the service
+ *   namespace's full name and then by traversing nested namespace segments.
+ *   Services that are not listed return `undefined` (meaning "use the latest
+ *   version").
  *
  * Multi-service packages do not support the special `all` value (in either the
  * string or the record form); it is ignored and treated as `undefined` (use the
@@ -1042,14 +1045,34 @@ export function resolveApiVersionForService(
     // multi-service packages do not support `all`.
     return isMultiService ? undefined : config;
   }
-  // Record case: map each service namespace's full name to a version.
+  // Map case: map each service namespace's full name or nested segments to a version.
   if (serviceNamespace === undefined) return undefined;
-  const version = config[getNamespaceFullName(serviceNamespace)];
+  const version = resolveApiVersionFromServiceMap(
+    config as ApiVersionServiceMap,
+    getNamespaceFullName(serviceNamespace),
+  );
   // Multi-service packages do not support `all`; fall back to the latest version.
   if (version === "all" && isMultiService) return undefined;
   return version;
 }
 
+function resolveApiVersionFromServiceMap(
+  config: ApiVersionServiceMap,
+  namespaceName: string,
+): string | undefined {
+  const flatVersion = config[namespaceName];
+  if (typeof flatVersion === "string") return flatVersion;
+
+  let current: string | ApiVersionServiceMap | undefined = config;
+  for (const segment of namespaceName.split(".")) {
+    if (typeof current !== "object" || current === null || Array.isArray(current)) {
+      return undefined;
+    }
+    current = current[segment];
+  }
+  return typeof current === "string" ? current : undefined;
+}
+
 /**
  * Find the service namespace that owns the given type. Starts from the type's
  * versioned namespace and walks up the enclosing namespaces until it reaches a
diff --git a/packages/typespec-client-generator-core/src/lib.ts b/packages/typespec-client-generator-core/src/lib.ts
index 67302bd7f4..425db9b322 100644
--- a/packages/typespec-client-generator-core/src/lib.ts
+++ b/packages/typespec-client-generator-core/src/lib.ts
@@ -11,7 +11,7 @@ import type {
 } from "./internal-utils.js";
 
 // `api-version` accepts either a string (single service / `latest` / `all`) or a
-// map from service namespace full name to version (multi-service).
+// map from service namespace names or nested namespace segments to versions.
 const apiVersionSchema = {
   oneOf: [
     {
@@ -20,13 +20,22 @@ const apiVersionSchema = {
     },
     {
       type: "object",
-      additionalProperties: { type: "string" },
+      additionalProperties: {
+        oneOf: [
+          { type: "string" },
+          {
+            type: "object",
+            additionalProperties: true,
+            required: [],
+          },
+        ],
+      },
       required: [],
       nullable: true,
     },
   ],
   description:
-    "Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.",
+    "Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.",
 } as any;
 
 export const UnbrandedSdkEmitterOptions = {
diff --git a/packages/typespec-client-generator-core/test/examples/load.test.ts b/packages/typespec-client-generator-core/test/examples/load.test.ts
index ded10fd711..6245285e90 100644
--- a/packages/typespec-client-generator-core/test/examples/load.test.ts
+++ b/packages/typespec-client-generator-core/test/examples/load.test.ts
@@ -469,6 +469,101 @@ it("multiple services without versioning", async () => {
   strictEqual(biMethod.operation.examples[0].name, "Test operation from ServiceB");
 });
 
+it("multiple nested services use configured api versions to find examples", async () => {
+  const instance = await SimpleBaseTester.createInstance();
+  instance.fs.addTypeSpecFile(
+    "./Network/examples/v1/NetworkOperations_get.json",
+    JSON.stringify({
+      operationId: "NetworkOperations_get",
+      title: "Network v1",
+      responses: { "200": { body: "network-v1" } },
+    }),
+  );
+  instance.fs.addTypeSpecFile(
+    "./Network/examples/v2/NetworkOperations_get.json",
+    JSON.stringify({
+      operationId: "NetworkOperations_get",
+      title: "Network v2",
+      responses: { "200": { body: "network-v2" } },
+    }),
+  );
+  instance.fs.addTypeSpecFile(
+    "./Compute/examples/v1/ComputeOperations_get.json",
+    JSON.stringify({
+      operationId: "ComputeOperations_get",
+      title: "Compute v1",
+      responses: { "200": { body: "compute-v1" } },
+    }),
+  );
+  instance.fs.addTypeSpecFile(
+    "./Compute/examples/v2/ComputeOperations_get.json",
+    JSON.stringify({
+      operationId: "ComputeOperations_get",
+      title: "Compute v2",
+      responses: { "200": { body: "compute-v2" } },
+    }),
+  );
+
+  const { program } = await instance.compile(
+    createClientCustomizationInput(
+      `
+      @service
+      @versioned(Microsoft.Network.Versions)
+      namespace Microsoft.Network {
+        enum Versions {
+          v1,
+          v2,
+        }
+        interface NetworkOperations {
+          op get(): string;
+        }
+      }
+
+      @service
+      @versioned(Microsoft.Compute.Versions)
+      namespace Microsoft.Compute {
+        enum Versions {
+          v1,
+          v2,
+        }
+        interface ComputeOperations {
+          op get(): string;
+        }
+      }
+    `,
+      `
+      @client({
+        name: "CombinedClient",
+        service: [Microsoft.Network, Microsoft.Compute],
+        autoMergeService: true,
+      })
+      namespace Combined;
+    `,
+    ),
+  );
+  const context = await createSdkContextForTester(program, {
+    "api-version": {
+      Microsoft: {
+        Network: "v1",
+        Compute: "v1",
+      },
+    },
+  });
+
+  const client = context.sdkPackage.clients[0];
+  const networkClient = client.children?.find((child) => child.name === "NetworkOperations");
+  ok(networkClient);
+  const networkMethod = networkClient.methods[0] as SdkServiceMethod<SdkHttpOperation>;
+  strictEqual(networkMethod.operation.examples?.[0].filePath, "v1/NetworkOperations_get.json");
+  strictEqual(networkMethod.operation.examples?.[0].name, "Network v1");
+
+  const computeClient = client.children?.find((child) => child.name === "ComputeOperations");
+  ok(computeClient);
+  const computeMethod = computeClient.methods[0] as SdkServiceMethod<SdkHttpOperation>;
+  strictEqual(computeMethod.operation.examples?.[0].filePath, "v1/ComputeOperations_get.json");
+  strictEqual(computeMethod.operation.examples?.[0].name, "Compute v1");
+});
+
 it("multiple services without examples", async () => {
   const { program } = await SimpleBaseTester.compile(
     createClientCustomizationInput(
diff --git a/packages/typespec-client-generator-core/test/package/api-versions-metadata.test.ts b/packages/typespec-client-generator-core/test/package/api-versions-metadata.test.ts
index 6edc2ee10a..755a8af4d1 100644
--- a/packages/typespec-client-generator-core/test/package/api-versions-metadata.test.ts
+++ b/packages/typespec-client-generator-core/test/package/api-versions-metadata.test.ts
@@ -1,5 +1,8 @@
+import { getDirectoryPath, resolveCompilerOptions } from "@typespec/compiler";
+import { resolveVirtualPath } from "@typespec/compiler/testing";
 import { deepStrictEqual, ok, strictEqual } from "assert";
 import { it } from "vitest";
+import { parse } from "yaml";
 import {
   createClientCustomizationInput,
   createSdkContextForTester,
@@ -36,6 +39,84 @@ it("single service with versioning should populate apiVersions map", async () =>
   strictEqual(sdkPackage.metadata.apiVersions.get("WidgetService"), "v3");
 });
 
+it("supports nested service namespaces in tspconfig.yaml", async () => {
+  const tester = await SimpleBaseTester.createInstance();
+  const spec = createClientCustomizationInput(
+    `
+      @service
+      @versioned(Microsoft.Network.Versions)
+      namespace Microsoft.Network {
+        enum Versions {
+          v1,
+          v2,
+        }
+        op networkTest(): void;
+      }
+
+      @service
+      @versioned(Microsoft.Compute.Versions)
+      namespace Microsoft.Compute {
+        enum Versions {
+          v1,
+          v2,
+        }
+        op computeTest(): void;
+      }
+    `,
+    `
+      @client({
+        name: "CombinedClient",
+        service: [Microsoft.Network, Microsoft.Compute],
+        autoMergeService: true,
+      })
+      namespace Combined;
+    `,
+  );
+  tester.fs.addTypeSpecFile("main.tsp", "");
+  tester.fs.addTypeSpecFile(
+    "tspconfig.yaml",
+    `
+emit:
+  - "@azure-tools/typespec-client-generator-core"
+options:
+  "@azure-tools/typespec-client-generator-core":
+    api-version:
+      Microsoft:
+        Network: v1
+        Compute: v1
+`,
+  );
+
+  const entrypoint = resolveVirtualPath("main.tsp");
+  const [compilerOptions, configDiagnostics] = await resolveCompilerOptions(
+    tester.fs.compilerHost,
+    {
+      cwd: getDirectoryPath(entrypoint),
+      entrypoint,
+    },
+  );
+  strictEqual(configDiagnostics.length, 0);
+
+  const [, diagnostics] = await tester.compileAndDiagnose(spec, {
+    compilerOptions,
+  });
+  strictEqual(
+    diagnostics.length,
+    0,
+    diagnostics.map((diagnostic) => diagnostic.message).join("\n"),
+  );
+
+  const output = [...tester.fs.fs.entries()].find(([path]) =>
+    path.endsWith("tcgc-output.yaml"),
+  )?.[1];
+  ok(output);
+  const sdkPackage = parse(output);
+  deepStrictEqual(sdkPackage.metadata.apiVersions, {
+    "Microsoft.Network": "v1",
+    "Microsoft.Compute": "v1",
+  });
+});
+
 it("multiple services should populate apiVersions map with all services", async () => {
   const { program } = await SimpleBaseTester.compile(
     createClientCustomizationInput(
diff --git a/packages/typespec-java/README.md b/packages/typespec-java/README.md
index fc2147cbeb..c5356c72dc 100644
--- a/packages/typespec-java/README.md
+++ b/packages/typespec-java/README.md
@@ -229,7 +229,7 @@ When set to `true`, the generated SDK uses `getter` method to access child clien
 
 **Type:** `string | object`
 
-Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.
+Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.
 
 **Options:**
 
diff --git a/packages/typespec-python/README.md b/packages/typespec-python/README.md
index afdff948ed..2f16a5c379 100644
--- a/packages/typespec-python/README.md
+++ b/packages/typespec-python/README.md
@@ -82,7 +82,7 @@ Whether to generate test files, for basic testing of your generated sdks. Defaul
 
 **Type:** `string | object`
 
-Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.
+Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.
 
 **Options:**
 
diff --git a/website/src/content/docs/docs/emitters/clients/typespec-java/reference/emitter.md b/website/src/content/docs/docs/emitters/clients/typespec-java/reference/emitter.md
index 7050e998a2..29c0996899 100644
--- a/website/src/content/docs/docs/emitters/clients/typespec-java/reference/emitter.md
+++ b/website/src/content/docs/docs/emitters/clients/typespec-java/reference/emitter.md
@@ -186,7 +186,7 @@ When set to `true`, the generated SDK uses `getter` method to access child clien
 
 **Type:** `string | object`
 
-Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.
+Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.
 
 **Options:**
 
diff --git a/website/src/content/docs/docs/emitters/clients/typespec-python/reference/emitter.md b/website/src/content/docs/docs/emitters/clients/typespec-python/reference/emitter.md
index acf829ab10..dcfe6779f2 100644
--- a/website/src/content/docs/docs/emitters/clients/typespec-python/reference/emitter.md
+++ b/website/src/content/docs/docs/emitters/clients/typespec-python/reference/emitter.md
@@ -76,7 +76,7 @@ Whether to generate test files, for basic testing of your generated sdks. Defaul
 
 **Type:** `string | object`
 
-Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.
+Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.
 
 **Options:**
 
diff --git a/website/src/content/docs/docs/libraries/typespec-client-generator-core/reference/emitter.md b/website/src/content/docs/docs/libraries/typespec-client-generator-core/reference/emitter.md
index d4c3e4ab8c..758d86b1d4 100644
--- a/website/src/content/docs/docs/libraries/typespec-client-generator-core/reference/emitter.md
+++ b/website/src/content/docs/docs/libraries/typespec-client-generator-core/reference/emitter.md
@@ -58,7 +58,7 @@ When set to `true`, the emitter will generate convenience methods for each servi
 
 **Type:** `string | object`
 
-Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace's full name to its desired version; services not listed default to their latest version.
+Use this flag if you would like to generate the sdk only for a specific version. Default value is the latest version. Also accepts values `latest` and `all`. For multi-service packages, provide a map from each service namespace to its desired version. Nested namespaces must be represented as nested objects in `tspconfig.yaml`; services not listed default to their latest version.
 
 **Options:**