diff --git a/.changeset/great-toys-knock.md b/.changeset/great-toys-knock.md
new file mode 100644
index 00000000..6c95a505
--- /dev/null
+++ b/.changeset/great-toys-knock.md
@@ -0,0 +1,5 @@
+---
+'@hono/auth-js': patch
+---
+
+fix(auth-js): use HonoRequest.blob() instead of HonoRequest.raw.body()
diff --git a/packages/auth-js/src/index.test.ts b/packages/auth-js/src/index.test.ts
index cfd82224..71eac417 100644
--- a/packages/auth-js/src/index.test.ts
+++ b/packages/auth-js/src/index.test.ts
@@ -2,6 +2,7 @@ import { skipCSRFCheck } from '@auth/core'
 import type { Adapter } from '@auth/core/adapters'
 import Credentials from '@auth/core/providers/credentials'
 import { Hono } from 'hono'
+import { validator } from 'hono/validator'
 import { describe, expect, it, vi } from 'vitest'
 import type { AuthConfig } from '.'
 import { authHandler, verifyAuth, initAuthConfig, reqWithEnvUrl } from '.'
@@ -80,6 +81,128 @@ describe('reqWithEnvUrl()', async () => {
   it('Should rewrite the base path', () => {
     expect(newReq.url.toString()).toBe('https://auth-url-base/request-path')
   })
+
+  const mockAdapter: Adapter = {
+    createVerificationToken: vi.fn(),
+    useVerificationToken: vi.fn(),
+    getUserByEmail: vi.fn(),
+    createUser: vi.fn(),
+    getUser: vi.fn(),
+    getUserByAccount: vi.fn(),
+    updateUser: vi.fn(),
+    linkAccount: vi.fn(),
+    createSession: vi.fn(),
+    getSessionAndUser: vi.fn(),
+    updateSession: vi.fn(),
+    deleteSession: vi.fn(),
+  }
+
+  globalThis.process.env = {
+    AUTH_SECRET: 'secret',
+  }
+
+  const user = { email: 'hono@hono.hono', name: 'Hono' }
+
+  const credentials = Credentials({
+    credentials: {
+      password: {},
+    },
+    authorize: (credentials) => {
+      if (credentials.password === 'password') {
+        return user
+      }
+      return null
+    },
+  })
+
+  function getAuthConfig(): AuthConfig {
+    return {
+      secret: 'secret',
+      providers: [credentials],
+      adapter: mockAdapter,
+      basePath: '/api/auth',
+      callbacks: {
+        jwt: ({ token, user }) => {
+          if (user) {
+            token.id = user.id
+          }
+          return token
+        },
+      },
+      session: {
+        strategy: 'jwt',
+      },
+    }
+  }
+
+  let cookie = ['']
+
+  it('Should be able to instantiate new Request after passing through validator', async () => {
+    const app = new Hono()
+
+    app.use('*', initAuthConfig(getAuthConfig))
+    app.use(
+      '/api/auth/*',
+      validator('form', (value, _) => {
+        const csrfToken = value['csrfToken']
+        return {
+          csrfToken,
+        }
+      }),
+      authHandler()
+    )
+
+    let csrfRes = await app.request('http://localhost/api/auth/csrf', {
+      method: 'GET',
+    })
+    let { csrfToken } = await csrfRes.json()
+
+    cookie = csrfRes.headers.getSetCookie()
+
+    let headers = new Headers()
+    headers.append('cookie', cookie[0])
+
+    const signInRes = await app.request('http://localhost/api/auth/callback/credentials', {
+      method: 'POST',
+      headers,
+      body: new URLSearchParams({
+        csrfToken,
+        password: 'password',
+      }),
+    })
+    expect(signInRes.status).toBe(302)
+    expect(signInRes.headers.get('location')).toBe('http://localhost')
+
+    cookie = signInRes.headers.getSetCookie()
+
+    const sessionCookie = cookie[1]
+
+    headers = new Headers()
+    headers.append('cookie', cookie[1])
+    headers.append('Content-Type', 'application/json')
+
+    csrfRes = await app.request('http://localhost/api/auth/csrf', {
+      method: 'GET',
+    })
+    ;({ csrfToken } = await csrfRes.json())
+
+    cookie = csrfRes.headers.getSetCookie()
+
+    headers = new Headers()
+    headers.append('cookie', cookie[0])
+    headers.append('cookie', sessionCookie)
+
+    const req = new Request('http://localhost/api/auth/signout', {
+      method: 'POST',
+      body: new URLSearchParams({
+        csrfToken,
+        password: 'password',
+      }),
+      headers,
+    })
+    const res = await app.request(req)
+    expect(res.status).toBe(302)
+  })
 })
 
 describe('Credentials Provider', () => {
diff --git a/packages/auth-js/src/index.ts b/packages/auth-js/src/index.ts
index ca0875a9..0944203c 100644
--- a/packages/auth-js/src/index.ts
+++ b/packages/auth-js/src/index.ts
@@ -135,7 +135,27 @@ export function authHandler(): MiddlewareHandler {
       throw new HTTPException(500, { message: 'Missing AUTH_SECRET' })
     }
 
-    const res = await Auth(reqWithEnvUrl(c.req.raw, ctxEnv.AUTH_URL), config)
+    const body = c.req.raw.body ? await c.req.blob() : undefined
+    const res = await Auth(
+      reqWithEnvUrl(
+        new Request(c.req.raw.url, {
+          body,
+          cache: c.req.raw.cache,
+          credentials: c.req.raw.credentials,
+          headers: c.req.raw.headers,
+          integrity: c.req.raw.integrity,
+          keepalive: c.req.raw.keepalive,
+          method: c.req.raw.method,
+          mode: c.req.raw.mode,
+          redirect: c.req.raw.redirect,
+          referrer: c.req.raw.referrer,
+          referrerPolicy: c.req.raw.referrerPolicy,
+          signal: c.req.raw.signal,
+        }),
+        ctxEnv.AUTH_URL
+      ),
+      config
+    )
     return new Response(res.body, res)
   }
 }