diff --git a/pkg/controller/backup_controller.go b/pkg/controller/backup_controller.go
index da915ed7e55..4a6656b8802 100644
--- a/pkg/controller/backup_controller.go
+++ b/pkg/controller/backup_controller.go
@@ -464,7 +464,7 @@ func (b *backupReconciler) prepareBackupRequest(backup *velerov1api.Backup, logg
 	}
 
 	// validate the included/excluded namespaces
-	for _, err := range collections.ValidateNamespaceIncludesExcludes(request.Spec.IncludedNamespaces, request.Spec.ExcludedNamespaces) {
+	for _, err := range b.validateNamespaceIncludesExcludes(request.Spec.IncludedNamespaces, request.Spec.ExcludedNamespaces) {
 		request.Status.ValidationErrors = append(request.Status.ValidationErrors, fmt.Sprintf("Invalid included/excluded namespace lists: %v", err))
 	}
 
@@ -601,6 +601,24 @@ func (b *backupReconciler) validateAndGetSnapshotLocations(backup *velerov1api.B
 	return providerLocations, nil
 }
 
+func (b *backupReconciler) validateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces []string) []error {
+	var errs []error
+	if errs = collections.ValidateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces); len(errs) > 0 {
+		return errs
+	}
+
+	namespace := &corev1api.Namespace{}
+	for _, name := range collections.NewIncludesExcludes().Includes(includedNamespaces...).GetIncludes() {
+		if name == "" || name == "*" {
+			continue
+		}
+		if err := b.kbClient.Get(context.Background(), kbclient.ObjectKey{Name: name}, namespace); err != nil {
+			errs = append(errs, err)
+		}
+	}
+	return errs
+}
+
 // runBackup runs and uploads a validated backup. Any error returned from this function
 // causes the backup to be Failed; if no error is returned, the backup's status's Errors
 // field is checked to see if the backup was a partial failure.
diff --git a/pkg/controller/backup_controller_test.go b/pkg/controller/backup_controller_test.go
index 7dd39229967..ccec0f899fb 100644
--- a/pkg/controller/backup_controller_test.go
+++ b/pkg/controller/backup_controller_test.go
@@ -1563,6 +1563,43 @@ func TestValidateAndGetSnapshotLocations(t *testing.T) {
 	}
 }
 
+func TestValidateNamespaceIncludesExcludes(t *testing.T) {
+	namespace := builder.ForNamespace("default").Result()
+	reconciler := &backupReconciler{
+		kbClient: velerotest.NewFakeControllerRuntimeClient(t, namespace),
+	}
+
+	// empty string as includedNamespaces
+	includedNamespaces := []string{""}
+	excludedNamespaces := []string{"test"}
+	errs := reconciler.validateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces)
+	assert.Empty(t, errs)
+
+	// "*" as includedNamespaces
+	includedNamespaces = []string{"*"}
+	excludedNamespaces = []string{"test"}
+	errs = reconciler.validateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces)
+	assert.Empty(t, errs)
+
+	// invalid namespaces
+	includedNamespaces = []string{"1@#"}
+	excludedNamespaces = []string{"2@#"}
+	errs = reconciler.validateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces)
+	assert.Len(t, errs, 2)
+
+	// not exist namespaces
+	includedNamespaces = []string{"non-existing-namespace"}
+	excludedNamespaces = []string{}
+	errs = reconciler.validateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces)
+	assert.Len(t, errs, 1)
+
+	// valid namespaces
+	includedNamespaces = []string{"default"}
+	excludedNamespaces = []string{}
+	errs = reconciler.validateNamespaceIncludesExcludes(includedNamespaces, excludedNamespaces)
+	assert.Empty(t, errs)
+}
+
 // Test_getLastSuccessBySchedule verifies that the getLastSuccessBySchedule helper function correctly returns
 // the completion timestamp of the most recent completed backup for each schedule, including an entry for ad-hoc
 // or non-scheduled backups.