diff --git a/types/index.d.ts b/types/index.d.ts
index 2de3e06..99af7f2 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -29,9 +29,9 @@ type FastifyAuth = FastifyPluginCallback<fastifyAuth.FastifyAuthPluginOptions>
 declare namespace fastifyAuth {
   export type FastifyAuthRelation = 'and' | 'or'
 
-  export type FastifyAuthFunction<
-    Request extends FastifyRequest = FastifyRequest,
-    Reply extends FastifyReply = FastifyReply
+  export type FastifyAuthSyncFunction<
+      Request extends FastifyRequest = FastifyRequest,
+      Reply extends FastifyReply = FastifyReply
   > = (
     this: FastifyInstance,
     request: Request,
@@ -39,6 +39,26 @@ declare namespace fastifyAuth {
     done: (error?: Error) => void
   ) => void
 
+  export type FastifyAuthAsyncFunction<
+      Request extends FastifyRequest = FastifyRequest,
+      Reply extends FastifyReply = FastifyReply
+  > = (
+    this: FastifyInstance,
+    request: Request,
+    reply: Reply
+  ) => Promise<void>
+
+  export type FastifyAuthFunction<
+      Request extends FastifyRequest = FastifyRequest,
+      Reply extends FastifyReply = FastifyReply,
+      Return extends
+      | ReturnType<FastifyAuthSyncFunction<Request, Reply>>
+      | ReturnType<FastifyAuthAsyncFunction<Request, Reply>>
+      = ReturnType<FastifyAuthSyncFunction<Request, Reply>>
+  > = Return extends ReturnType<FastifyAuthSyncFunction<Request, Reply>>
+    ? FastifyAuthSyncFunction<Request, Reply>
+    : FastifyAuthAsyncFunction<Request, Reply>
+
   /**
    * @link [`fastify-auth` options documentation](https://github.com/fastify/fastify-auth#options)
    */
diff --git a/types/index.test-d.ts b/types/index.test-d.ts
index 44c44be..158f9f7 100644
--- a/types/index.test-d.ts
+++ b/types/index.test-d.ts
@@ -9,6 +9,7 @@ const app = fastify()
 type Done = (error?: Error) => void
 
 app.register(fastifyAuth).after((_err) => {
+  // Callback tests
   app.auth([
     (request, reply, done) => {
       expectType<FastifyRequest>(request)
@@ -16,6 +17,13 @@ app.register(fastifyAuth).after((_err) => {
       expectType<Done>(done)
     },
   ], { relation: 'or' })
+  app.auth([
+    (request, reply, done) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      expectType<Done>(done)
+    },
+  ], { relation: 'and' })
   app.auth([
     (request, reply, done) => {
       expectType<FastifyRequest>(request)
@@ -29,12 +37,123 @@ app.register(fastifyAuth).after((_err) => {
       expectType<FastifyReply>(reply)
       expectType<Done>(done)
     },
+  ], { relation: 'or', run: 'all' })
+  app.auth([
+    (request, reply, done) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      expectType<Done>(done)
+    },
+  ], { relation: 'and', run: 'all' })
+
+  // Async function tests
+  app.auth([
+    async (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      await Promise.resolve()
+    },
+  ])
+  app.auth([
+    async (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      await Promise.resolve()
+    },
+  ], { relation: 'or' })
+  app.auth([
+    async (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      await Promise.resolve()
+    },
+  ], { relation: 'and' })
+  app.auth([
+    async (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      await Promise.resolve()
+    },
+  ], { run: 'all' })
+  app.auth([
+    async (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      await Promise.resolve()
+    },
+  ], { relation: 'or', run: 'all' })
+  app.auth([
+    async (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      await Promise.resolve()
+    },
+  ], { relation: 'and', run: 'all' })
+
+  // Promise-based function tests
+  app.auth([
+    (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      return Promise.resolve()
+    },
+  ])
+  app.auth([
+    (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      return Promise.resolve()
+    },
+  ], { relation: 'or' })
+  app.auth([
+    (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      return Promise.resolve()
+    },
+  ], { relation: 'and' })
+  app.auth([
+    (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      return Promise.resolve()
+    },
+  ], { run: 'all' })
+  app.auth([
+    (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      return Promise.resolve()
+    },
+  ], { relation: 'or', run: 'all' })
+  app.auth([
+    (request: FastifyRequest, reply: FastifyReply) => {
+      expectType<FastifyRequest>(request)
+      expectType<FastifyReply>(reply)
+      return Promise.resolve()
+    },
+  ], { relation: 'and', run: 'all' })
+
+  // this context tests
+  app.auth([
+    async function () {
+      expectType<FastifyInstance>(this)
+      await Promise.resolve()
+    },
   ])
   app.auth([
     function () {
       expectType<FastifyInstance>(this)
+      return Promise.resolve()
     },
   ])
+  app.auth([
+    async function () {
+      expectType<FastifyInstance>(this)
+      await Promise.resolve()
+    },
+  ])
+
   const auth = app.auth([() => {}])
   expectType<preHandlerHookHandler>(auth)
   app.get('/secret', { preHandler: auth }, () => {})