diff --git a/.changeset/nine-cherries-decide.md b/.changeset/nine-cherries-decide.md
new file mode 100644
index 0000000000..b20c24aa85
--- /dev/null
+++ b/.changeset/nine-cherries-decide.md
@@ -0,0 +1,14 @@
+---
+'@backstage/backend-common': patch
+---
+
+The remaining exports in the package have now been deprecated:
+
+- `cacheToPluginCacheManager`
+- `createLegacyAuthAdapters`
+- `LegacyCreateRouter`
+- `legacyPlugin`
+- `loggerToWinstonLogger`
+- `makeLegacyPlugin`
+
+Users of these export should fully [migrate to the new backend system](https://backstage.io/docs/backend-system/building-backends/migrating).
diff --git a/packages/backend-common/api-report.md b/packages/backend-common/api-report.md
index 52b661bcaf..23ed13b62c 100644
--- a/packages/backend-common/api-report.md
+++ b/packages/backend-common/api-report.md
@@ -129,7 +129,7 @@ export class CacheManager extends CacheManager_2 {}
 // @public @deprecated (undocumented)
 export type CacheManagerOptions = CacheManagerOptions_2;
 
-// @public
+// @public @deprecated
 export function cacheToPluginCacheManager(cache: CacheService): {
   getClient(options?: CacheServiceOptions): CacheService;
 };
@@ -142,7 +142,7 @@ export interface ContainerRunner {
   runContainer(opts: RunContainerOptions): Promise<void>;
 }
 
-// @public
+// @public @deprecated
 export function createLegacyAuthAdapters<
   TOptions extends {
     auth?: AuthService;
@@ -401,10 +401,10 @@ export type KubernetesContainerRunnerOptions = {
   timeoutMs?: number;
 };
 
-// @public (undocumented)
+// @public @deprecated (undocumented)
 export type LegacyCreateRouter<TEnv> = (deps: TEnv) => Promise<RequestHandler>;
 
-// @public
+// @public @deprecated
 export const legacyPlugin: (
   name: string,
   createRouterImport: Promise<{
@@ -447,13 +447,13 @@ export function loadBackendConfig(options: {
   watch?: boolean;
 }): Promise<Config>;
 
-// @public (undocumented)
+// @public @deprecated (undocumented)
 export function loggerToWinstonLogger(
   logger: LoggerService,
   opts?: TransportStreamOptions,
 ): Logger;
 
-// @public
+// @public @deprecated
 export function makeLegacyPlugin<
   TEnv extends Record<string, unknown>,
   TEnvTransforms extends {
diff --git a/packages/backend-common/src/compat/auth/createLegacyAuthAdapters.ts b/packages/backend-common/src/compat/auth/createLegacyAuthAdapters.ts
index 0f591eac6c..15cd881649 100644
--- a/packages/backend-common/src/compat/auth/createLegacyAuthAdapters.ts
+++ b/packages/backend-common/src/compat/auth/createLegacyAuthAdapters.ts
@@ -292,6 +292,7 @@ export class UserInfoCompat implements UserInfoService {
 /**
  * An adapter that ensures presence of the auth and/or httpAuth services.
  * @public
+ * @deprecated Migrate to use the new backend system and auth services instead.
  */
 export function createLegacyAuthAdapters<
   TOptions extends {
diff --git a/packages/backend-common/src/compat/cache/cacheToPluginCacheManager.ts b/packages/backend-common/src/compat/cache/cacheToPluginCacheManager.ts
index 2654934804..2ae55b016f 100644
--- a/packages/backend-common/src/compat/cache/cacheToPluginCacheManager.ts
+++ b/packages/backend-common/src/compat/cache/cacheToPluginCacheManager.ts
@@ -24,6 +24,7 @@ import {
  * old-backend plugin cache manager.
  *
  * @public
+ * @deprecated Migrate to use the new CacheService instead.
  */
 export function cacheToPluginCacheManager(cache: CacheService): {
   getClient(options?: CacheServiceOptions): CacheService;
diff --git a/packages/backend-common/src/compat/legacy/legacy.ts b/packages/backend-common/src/compat/legacy/legacy.ts
index 57220a8430..c779daacd2 100644
--- a/packages/backend-common/src/compat/legacy/legacy.ts
+++ b/packages/backend-common/src/compat/legacy/legacy.ts
@@ -27,6 +27,7 @@ import { TokenManager } from '../../deprecated';
 
 /**
  * @public
+ * @deprecated Fully use the new backend system instead.
  */
 export type LegacyCreateRouter<TEnv> = (deps: TEnv) => Promise<RequestHandler>;
 
@@ -69,6 +70,7 @@ function wrapTokenManager(tokenManager: TokenManager, auth: AuthService) {
  * Creates a new custom plugin compatibility wrapper.
  *
  * @public
+ * @deprecated Fully use the new backend system instead.
  * @remarks
  *
  * Usually you can use {@link legacyPlugin} directly instead, but you might
@@ -128,6 +130,7 @@ export function makeLegacyPlugin<
  * register it with the http router based on the plugin id.
  *
  * @public
+ * @deprecated Fully use the new backend system instead.
  * @remarks
  *
  * This is intended to be used by plugin authors to ease the transition to the
diff --git a/packages/backend-common/src/compat/logging/loggerToWinstonLogger.ts b/packages/backend-common/src/compat/logging/loggerToWinstonLogger.ts
index 4ba88358d2..83871f48e3 100644
--- a/packages/backend-common/src/compat/logging/loggerToWinstonLogger.ts
+++ b/packages/backend-common/src/compat/logging/loggerToWinstonLogger.ts
@@ -53,7 +53,10 @@ class BackstageLoggerTransport extends Transport {
   }
 }
 
-/** @public */
+/**
+ * @public
+ * @deprecated Migrate to use the new LoggerService instead.
+ */
 export function loggerToWinstonLogger(
   logger: LoggerService,
   opts?: TransportStreamOptions,