diff --git a/plugins/auth-backend/src/lib/legacy/adoptLegacyOAuthSignInResolver.test.ts b/plugins/auth-backend/src/lib/legacy/adoptLegacyOAuthSignInResolver.test.ts
new file mode 100644
index 0000000000..ab18970918
--- /dev/null
+++ b/plugins/auth-backend/src/lib/legacy/adoptLegacyOAuthSignInResolver.test.ts
@@ -0,0 +1,69 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  AuthResolverContext,
+  PassportProfile,
+} from '@backstage/plugin-auth-node';
+import { adoptLegacyOAuthSignInResolver } from './adoptLegacyOAuthSignInResolver';
+
+describe('adoptLegacyOAuthSignInResolver', () => {
+  it('should pass through undefined', () => {
+    expect(adoptLegacyOAuthSignInResolver(undefined)).toBeUndefined();
+  });
+
+  it('should convert a legacy resolver to a new one', () => {
+    const legacyResolver = jest.fn();
+
+    const newResolver = adoptLegacyOAuthSignInResolver(legacyResolver);
+
+    newResolver?.(
+      {
+        profile: { email: 'em@i.l' },
+        result: {
+          fullProfile: { id: 'id' } as PassportProfile,
+          session: {
+            accessToken: 'token',
+            expiresInSeconds: 3,
+            scope: 'sco pe',
+            tokenType: 'bear',
+            idToken: 'id-token',
+            refreshToken: 'refresh-token',
+          },
+        },
+      },
+      { ctx: 'ctx' } as unknown as AuthResolverContext,
+    );
+
+    expect(legacyResolver).toHaveBeenCalledWith(
+      {
+        profile: { email: 'em@i.l' },
+        result: {
+          fullProfile: { id: 'id' },
+          accessToken: 'token',
+          refreshToken: 'refresh-token',
+          params: {
+            scope: 'sco pe',
+            id_token: 'id-token',
+            expires_in: 3,
+            token_type: 'bear',
+          },
+        },
+      },
+      { ctx: 'ctx' },
+    );
+  });
+});
diff --git a/plugins/auth-backend/src/lib/legacy/adoptLegacyOAuthSignInResolver.ts b/plugins/auth-backend/src/lib/legacy/adoptLegacyOAuthSignInResolver.ts
new file mode 100644
index 0000000000..594c296374
--- /dev/null
+++ b/plugins/auth-backend/src/lib/legacy/adoptLegacyOAuthSignInResolver.ts
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  OAuthAuthenticatorResult,
+  PassportProfile,
+  SignInResolver,
+} from '@backstage/plugin-auth-node';
+import { OAuthResult } from '../oauth';
+
+/** @public */
+export function adoptLegacyOAuthSignInResolver(
+  signInResolver?: SignInResolver<OAuthResult>,
+): SignInResolver<OAuthAuthenticatorResult<PassportProfile>> | undefined {
+  return (
+    signInResolver &&
+    (async (input, ctx) =>
+      signInResolver(
+        {
+          profile: input.profile,
+          result: {
+            fullProfile: input.result.fullProfile,
+            accessToken: input.result.session.accessToken,
+            refreshToken: input.result.session.refreshToken,
+            params: {
+              scope: input.result.session.scope,
+              id_token: input.result.session.idToken,
+              token_type: input.result.session.tokenType,
+              expires_in: input.result.session.expiresInSeconds,
+            },
+          },
+        },
+        ctx,
+      ))
+  );
+}
diff --git a/plugins/auth-backend/src/lib/legacy/index.ts b/plugins/auth-backend/src/lib/legacy/index.ts
index b05f9afdab..44bbae998c 100644
--- a/plugins/auth-backend/src/lib/legacy/index.ts
+++ b/plugins/auth-backend/src/lib/legacy/index.ts
@@ -15,3 +15,4 @@
  */
 
 export { adaptLegacyOAuthHandler } from './adaptLegacyOAuthHandler';
+export { adoptLegacyOAuthSignInResolver } from './adoptLegacyOAuthSignInResolver';