diff --git a/services-api/pkg/service/iam/auth.go b/services-api/pkg/service/iam/auth.go
index 5db700d0c..71a0d3e76 100644
--- a/services-api/pkg/service/iam/auth.go
+++ b/services-api/pkg/service/iam/auth.go
@@ -538,7 +538,13 @@ func (o *OAuth20Service) ParseAccessTokenToClaims(accessToken string, validate b
 			}
 		}
 
-		errValidate := o.Validate(accessToken, perm, &claims.Namespace, nil)
+		namespace := claims.Namespace
+
+		if claims.ExtendNamespace != "" {
+			namespace = claims.ExtendNamespace
+		}
+
+		errValidate := o.Validate(accessToken, perm, &namespace, nil)
 		if errValidate != nil {
 			log.Fatalf("token validation failed: %s", errValidate.Error())
 		}
diff --git a/services-api/pkg/service/iam/auth_validator.go b/services-api/pkg/service/iam/auth_validator.go
index 23bcdc495..fb70d798e 100644
--- a/services-api/pkg/service/iam/auth_validator.go
+++ b/services-api/pkg/service/iam/auth_validator.go
@@ -104,6 +104,10 @@ func (v *TokenValidator) Validate(token string, permission *Permission, namespac
 		}
 		fmt.Println("token verified")
 
+		if errNamespace := v.hasValidNamespace(v.JwtClaims, namespace); errNamespace != nil {
+			return errors.New(errNamespace.Error())
+		}
+
 		if !v.hasValidPermissions(v.JwtClaims, permission, namespace, userId) {
 			return errors.New("insufficient permissions")
 		}
@@ -124,6 +128,10 @@ func (v *TokenValidator) Validate(token string, permission *Permission, namespac
 		return errors.New("user was revoked")
 	}
 
+	if errNamespace := v.hasValidNamespace(v.JwtClaims, namespace); errNamespace != nil {
+		return errors.New(errNamespace.Error())
+	}
+
 	if !v.hasValidPermissions(v.JwtClaims, permission, namespace, userId) {
 		return errors.New("insufficient permissions")
 	}
@@ -377,6 +385,20 @@ func (v *TokenValidator) hasValidPermissions(claims JWTClaims, permission *Permi
 	return false
 }
 
+func (v *TokenValidator) hasValidNamespace(claims JWTClaims, namespace *string) error {
+	if namespace == nil {
+		return fmt.Errorf("trying to validate access token against a namepace, but have an empty namespace")
+	}
+
+	if claims.ExtendNamespace != "" {
+		if claims.ExtendNamespace != *namespace {
+			return fmt.Errorf("extend namespace from token has different a namespace with grpc server")
+		}
+	}
+
+	return nil
+}
+
 func (v *TokenValidator) isTokenRevoked(token string) bool {
 	return v.Filter.MightContain([]byte(token))
 }
diff --git a/services-api/pkg/service/iam/auth_validator_test.go b/services-api/pkg/service/iam/auth_validator_test.go
index e02b7d623..cb9cd1cf3 100644
--- a/services-api/pkg/service/iam/auth_validator_test.go
+++ b/services-api/pkg/service/iam/auth_validator_test.go
@@ -6,8 +6,10 @@ package iam
 
 import (
 	"fmt"
+	"os"
 	"testing"
 
+	"github.com/AccelByte/accelbyte-go-sdk/iam-sdk/pkg/iamclient/o_auth2_0"
 	"github.com/AccelByte/accelbyte-go-sdk/services-api/pkg/factory"
 	"github.com/AccelByte/accelbyte-go-sdk/services-api/pkg/utils/auth"
 	"github.com/stretchr/testify/assert"
@@ -40,7 +42,7 @@ func TestTokenValidator_ValidateToken(t *testing.T) {
 		return
 	}
 
-	namespace := "accelbyte"
+	namespace := os.Getenv("AB_NAMESPACE")
 	resourceName := "MMV2GRPCSERVICE"
 	requiredPermission := Permission{
 		Action:   2,
@@ -62,3 +64,44 @@ func TestTokenValidator_ValidateToken(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, claims.Namespace, namespace)
 }
+
+func TestTokenValidator_ValidateExtendNamespace(t *testing.T) {
+	// should be moved and run as integration test, skip for now
+	t.Skip()
+
+	// Arrange
+	configRepo := auth.DefaultConfigRepositoryImpl()
+	tokenRepo := auth.DefaultTokenRepositoryImpl()
+	authService := OAuth20Service{
+		Client:           factory.NewIamClient(configRepo),
+		ConfigRepository: configRepo,
+		TokenRepository:  tokenRepo,
+	}
+
+	extendNamespace := os.Getenv("AB_NAMESPACE")
+
+	token, err := authService.TokenGrantV3Short(&o_auth2_0.TokenGrantV3Params{
+		ExtendNamespace: &extendNamespace,
+		GrantType:       o_auth2_0.TokenGrantV3UrnIetfParamsOauthGrantTypeExtendClientCredentialsConstant,
+	})
+	if err != nil {
+		assert.Fail(t, err.Error())
+
+		return
+	}
+
+	authService.SetLocalValidation(false)                                                // true will do it locally, false will do it remotely
+	claims, errClaims := authService.ParseAccessTokenToClaims(*token.AccessToken, false) // false will not validate at all, only claim. This test will validate in the next line
+	if errClaims != nil {
+		assert.Fail(t, errClaims.Error())
+
+		return
+	}
+
+	// Act
+	err = authService.Validate(*token.AccessToken, nil, &extendNamespace, nil) // validate against the extend namespace
+
+	// Assert
+	assert.Nil(t, err)
+	assert.Equal(t, claims.ExtendNamespace, extendNamespace)
+}