diff --git a/tools/testing/kata-webhook/main.go b/tools/testing/kata-webhook/main.go
index 8e040d60df..bdf2fe2a18 100644
--- a/tools/testing/kata-webhook/main.go
+++ b/tools/testing/kata-webhook/main.go
@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"regexp"
 	"strings"
 
 	corev1 "k8s.io/api/core/v1"
@@ -44,6 +45,11 @@ func annotatePodMutator(_ context.Context, ar *kwhmodel.AdmissionReview, obj met
 		fmt.Println("blacklisted namespace: ", ar.Namespace)
 		return &kwhmutating.MutatorResult{}, nil
 	}
+	// Check if we are only mutating pods in specific namespaces using the regular expression.
+	if whPolicy.nsOnlyRegexp != nil && !whPolicy.nsOnlyRegexp.MatchString(ar.Namespace) {
+		fmt.Println("namespace doesn't match re-only-namespaces: ", ar.Namespace)
+		return &kwhmutating.MutatorResult{}, nil
+	}
 
 	// We cannot support --net=host in Kata
 	// https://github.com/kata-containers/documentation/blob/master/Limitations.md#docker---nethost
@@ -84,13 +90,15 @@ func annotatePodMutator(_ context.Context, ar *kwhmodel.AdmissionReview, obj met
 }
 
 type config struct {
-	certFile    string
-	keyFile     string
-	nsBlacklist string
+	certFile     string
+	keyFile      string
+	nsBlacklist  string
+	nsOnlyRegexp string
 }
 
 type policy struct {
-	nsBlacklist map[string]bool
+	nsBlacklist  map[string]bool
+	nsOnlyRegexp *regexp.Regexp
 }
 
 var whPolicy *policy
@@ -102,6 +110,7 @@ func initFlags() *config {
 	fl.StringVar(&cfg.certFile, "tls-cert-file", "", "TLS certificate file")
 	fl.StringVar(&cfg.keyFile, "tls-key-file", "", "TLS key file")
 	fl.StringVar(&cfg.nsBlacklist, "exclude-namespaces", "", "Comma separated namespace blacklist")
+	fl.StringVar(&cfg.nsOnlyRegexp, "only-namespaces-regexp", "", "Regexp namespace filter applied after --exclude-namespaces")
 
 	fl.Parse(os.Args[1:])
 	return cfg
@@ -122,6 +131,15 @@ func main() {
 		}
 	}
 
+	if cfg.nsOnlyRegexp != "" {
+		var err error
+		whPolicy.nsOnlyRegexp, err = regexp.Compile(cfg.nsOnlyRegexp)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error compiling regular expression: %s", err)
+			os.Exit(1)
+		}
+	}
+
 	// Create our mutator
 	mt := kwhmutating.MutatorFunc(annotatePodMutator)
 
diff --git a/tools/testing/kata-webhook/main_test.go b/tools/testing/kata-webhook/main_test.go
new file mode 100644
index 0000000000..0378f203ad
--- /dev/null
+++ b/tools/testing/kata-webhook/main_test.go
@@ -0,0 +1,60 @@
+// Copyright (c) 2025 Red Hat Inc.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"context"
+	"regexp"
+	"testing"
+
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	kwhmodel "github.com/slok/kubewebhook/v2/pkg/model"
+)
+
+func TestAnnotatePodMutator(t *testing.T) {
+	tests := []struct {
+		name         string
+		nsBlacklist  map[string]bool
+		nsOnlyRegexp *regexp.Regexp
+		wantMutated  bool
+	}{
+		{"no filters", nil, nil, true},
+		{"matching nsBlacklist", map[string]bool{"testing-namespace": true}, nil, false},
+		{"matching nsOnlyRegexp", nil, regexp.MustCompile("^testing-.*$"), true},
+		{"nonmatching nsOnlyRegexp", nil, regexp.MustCompile(".*nonexisting.*"), false},
+	}
+
+	expectedRuntimeClass := "kata"
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			whPolicy = &policy{nsBlacklist: tt.nsBlacklist, nsOnlyRegexp: tt.nsOnlyRegexp}
+
+			pod := &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "testing-namespace",
+				},
+			}
+
+			ar := &kwhmodel.AdmissionReview{
+				Namespace: "testing-namespace",
+			}
+
+			result, err := annotatePodMutator(context.Background(), ar, pod)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			mutated := result.MutatedObject != nil && result.MutatedObject.(*corev1.Pod).Spec.RuntimeClassName != nil
+			if mutated != tt.wantMutated {
+				t.Errorf("expected mutation: %v, got: %v", tt.wantMutated, mutated)
+			}
+			if mutated && *result.MutatedObject.(*corev1.Pod).Spec.RuntimeClassName != expectedRuntimeClass {
+				t.Errorf("expected runtimeclass: %v, got %v", expectedRuntimeClass, result.MutatedObject.(*corev1.Pod).Spec.RuntimeClassName)
+			}
+		})
+	}
+}