diff --git a/src/runtime/server/lib/oauth/zitadel.ts b/src/runtime/server/lib/oauth/zitadel.ts
index 9a073518..c2a85993 100644
--- a/src/runtime/server/lib/oauth/zitadel.ts
+++ b/src/runtime/server/lib/oauth/zitadel.ts
@@ -2,7 +2,8 @@ import type { H3Event } from 'h3'
 import { eventHandler, getQuery, sendRedirect } from 'h3'
 import { withQuery } from 'ufo'
 import { defu } from 'defu'
-import { handleMissingConfiguration, handleAccessTokenErrorResponse, getOAuthRedirectURL, requestAccessToken } from '../utils'
+import type { RequestAccessTokenOptions } from '../utils'
+import { handleMissingConfiguration, handleAccessTokenErrorResponse, getOAuthRedirectURL, requestAccessToken, handleState, handlePkceVerifier, handleInvalidState } from '../utils'
 import { useRuntimeConfig, createError } from '#imports'
 import type { OAuthConfig } from '#auth-utils'
 
@@ -48,7 +49,7 @@ export function defineOAuthZitadelEventHandler({ config, onSuccess, onError }: O
       authorizationParams: {},
     }) as OAuthZitadelConfig
 
-    const query = getQuery<{ code?: string, error?: string }>(event)
+    const query = getQuery<{ code?: string, state?: string, error?: string }>(event)
 
     if (query.error) {
       const error = createError({
@@ -60,14 +61,18 @@ export function defineOAuthZitadelEventHandler({ config, onSuccess, onError }: O
       return onError(event, error)
     }
 
-    if (!config.clientId || !config.clientSecret || !config.domain) {
-      return handleMissingConfiguration(event, 'zitadel', ['clientId', 'clientSecret', 'issuerUrl'], onError)
+    if (!config.clientId || !config.domain) {
+      return handleMissingConfiguration(event, 'zitadel', ['clientId', 'domain'], onError)
     }
 
     const authorizationURL = `https://${config.domain}/oauth/v2/authorize`
     const tokenURL = `https://${config.domain}/oauth/v2/token`
     const redirectURL = config.redirectURL || getOAuthRedirectURL(event)
 
+    // Create pkce verifier
+    const verifier = await handlePkceVerifier(event)
+    const state = await handleState(event)
+
     if (!query.code) {
       config.scope = config.scope || ['openid']
       // Redirect to Zitadel OAuth page
@@ -79,23 +84,37 @@ export function defineOAuthZitadelEventHandler({ config, onSuccess, onError }: O
           client_id: config.clientId,
           redirect_uri: redirectURL,
           scope: config.scope.join(' '),
+          state,
+          code_challenge: verifier.code_challenge,
+          code_challenge_method: verifier.code_challenge_method,
           ...config.authorizationParams,
         }),
       )
     }
 
-    const tokens = await requestAccessToken(tokenURL, {
-      headers: {
-        'Authorization': `Basic ${Buffer.from(`${config.clientId}:${config.clientSecret}`).toString('base64')}`,
-        'Content-Type': 'application/x-www-form-urlencoded',
-      },
+    if (query.state !== state) {
+      return handleInvalidState(event, 'zitadel', onError)
+    }
+
+    const request: RequestAccessTokenOptions = {
       body: {
         grant_type: 'authorization_code',
         client_id: config.clientId,
         redirect_uri: redirectURL,
         code: query.code,
+        code_verifier: verifier.code_verifier,
       },
-    })
+    }
+
+    if (config.clientSecret) {
+      const basicAuthorization = Buffer.from(`${config.clientId}:${config.clientSecret}`).toString('base64')
+      request.headers = {
+        'Authorization': `Basic ${basicAuthorization}`,
+        'Content-Type': 'application/x-www-form-urlencoded',
+      }
+    }
+
+    const tokens = await requestAccessToken(tokenURL, request)
 
     if (tokens.error) {
       return handleAccessTokenErrorResponse(event, 'zitadel', tokens, onError)
diff --git a/src/runtime/server/lib/utils.ts b/src/runtime/server/lib/utils.ts
index eb631469..699eda29 100644
--- a/src/runtime/server/lib/utils.ts
+++ b/src/runtime/server/lib/utils.ts
@@ -27,7 +27,7 @@ export interface RequestAccessTokenBody {
   [key: string]: string | undefined
 }
 
-interface RequestAccessTokenOptions {
+export interface RequestAccessTokenOptions {
   body?: RequestAccessTokenBody
   params?: Record<string, string | undefined>
   headers?: Record<string, string>