diff --git a/cmd/k8s-operator/operator_test.go b/cmd/k8s-operator/operator_test.go
index 21e1d4313..a440fafb5 100644
--- a/cmd/k8s-operator/operator_test.go
+++ b/cmd/k8s-operator/operator_test.go
@@ -432,6 +432,148 @@ func TestTailnetTargetIPAnnotation(t *testing.T) {
 	expectMissing[corev1.Secret](t, fc, "operator-ns", fullName)
 }
 
+func TestTailnetTargetIPAnnotation_IPCouldNotBeParsed(t *testing.T) {
+	fc := fake.NewFakeClient()
+	ft := &fakeTSClient{}
+	zl, err := zap.NewDevelopment()
+	if err != nil {
+		t.Fatal(err)
+	}
+	clock := tstest.NewClock(tstest.ClockOpts{})
+	sr := &ServiceReconciler{
+		Client: fc,
+		ssr: &tailscaleSTSReconciler{
+			Client:            fc,
+			tsClient:          ft,
+			defaultTags:       []string{"tag:k8s"},
+			operatorNamespace: "operator-ns",
+			proxyImage:        "tailscale/tailscale",
+		},
+		logger:   zl.Sugar(),
+		clock:    clock,
+		recorder: record.NewFakeRecorder(100),
+	}
+	tailnetTargetIP := "invalid-ip"
+	mustCreate(t, fc, &corev1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "test",
+			Namespace: "default",
+
+			UID: types.UID("1234-UID"),
+			Annotations: map[string]string{
+				AnnotationTailnetTargetIP: tailnetTargetIP,
+			},
+		},
+		Spec: corev1.ServiceSpec{
+			ClusterIP:         "10.20.30.40",
+			Type:              corev1.ServiceTypeLoadBalancer,
+			LoadBalancerClass: ptr.To("tailscale"),
+		},
+	})
+
+	expectReconciled(t, sr, "default", "test")
+
+	t0 := conditionTime(clock)
+
+	want := &corev1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "test",
+			Namespace: "default",
+			UID:       types.UID("1234-UID"),
+			Annotations: map[string]string{
+				AnnotationTailnetTargetIP: tailnetTargetIP,
+			},
+		},
+		Spec: corev1.ServiceSpec{
+			ClusterIP:         "10.20.30.40",
+			Type:              corev1.ServiceTypeLoadBalancer,
+			LoadBalancerClass: ptr.To("tailscale"),
+		},
+		Status: corev1.ServiceStatus{
+			Conditions: []metav1.Condition{{
+				Type:               string(tsapi.ProxyReady),
+				Status:             metav1.ConditionFalse,
+				LastTransitionTime: t0,
+				Reason:             reasonProxyInvalid,
+				Message:            `unable to provision proxy resources: invalid Service: invalid value of annotation tailscale.com/tailnet-ip: "invalid-ip" could not be parsed as a valid IP Address, error: ParseAddr("invalid-ip"): unable to parse IP`,
+			}},
+		},
+	}
+
+	expectEqual(t, fc, want, nil)
+}
+
+func TestTailnetTargetIPAnnotation_InvalidIP(t *testing.T) {
+	fc := fake.NewFakeClient()
+	ft := &fakeTSClient{}
+	zl, err := zap.NewDevelopment()
+	if err != nil {
+		t.Fatal(err)
+	}
+	clock := tstest.NewClock(tstest.ClockOpts{})
+	sr := &ServiceReconciler{
+		Client: fc,
+		ssr: &tailscaleSTSReconciler{
+			Client:            fc,
+			tsClient:          ft,
+			defaultTags:       []string{"tag:k8s"},
+			operatorNamespace: "operator-ns",
+			proxyImage:        "tailscale/tailscale",
+		},
+		logger:   zl.Sugar(),
+		clock:    clock,
+		recorder: record.NewFakeRecorder(100),
+	}
+	tailnetTargetIP := "999.999.999.999"
+	mustCreate(t, fc, &corev1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "test",
+			Namespace: "default",
+
+			UID: types.UID("1234-UID"),
+			Annotations: map[string]string{
+				AnnotationTailnetTargetIP: tailnetTargetIP,
+			},
+		},
+		Spec: corev1.ServiceSpec{
+			ClusterIP:         "10.20.30.40",
+			Type:              corev1.ServiceTypeLoadBalancer,
+			LoadBalancerClass: ptr.To("tailscale"),
+		},
+	})
+
+	expectReconciled(t, sr, "default", "test")
+
+	t0 := conditionTime(clock)
+
+	want := &corev1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "test",
+			Namespace: "default",
+			UID:       types.UID("1234-UID"),
+			Annotations: map[string]string{
+				AnnotationTailnetTargetIP: tailnetTargetIP,
+			},
+		},
+		Spec: corev1.ServiceSpec{
+			ClusterIP:         "10.20.30.40",
+			Type:              corev1.ServiceTypeLoadBalancer,
+			LoadBalancerClass: ptr.To("tailscale"),
+		},
+		Status: corev1.ServiceStatus{
+			Conditions: []metav1.Condition{{
+				Type:               string(tsapi.ProxyReady),
+				Status:             metav1.ConditionFalse,
+				LastTransitionTime: t0,
+				Reason:             reasonProxyInvalid,
+				Message:            `unable to provision proxy resources: invalid Service: invalid value of annotation tailscale.com/tailnet-ip: "999.999.999.999" could not be parsed as a valid IP Address, error: ParseAddr("999.999.999.999"): IPv4 field has value >255`,
+			}},
+		},
+	}
+
+	expectEqual(t, fc, want, nil)
+}
+
 func TestAnnotations(t *testing.T) {
 	fc := fake.NewFakeClient()
 	ft := &fakeTSClient{}
diff --git a/cmd/k8s-operator/svc.go b/cmd/k8s-operator/svc.go
index f45f92246..3c6bc27a9 100644
--- a/cmd/k8s-operator/svc.go
+++ b/cmd/k8s-operator/svc.go
@@ -358,9 +358,14 @@ func validateService(svc *corev1.Service) []string {
 			violations = append(violations, fmt.Sprintf("invalid value of annotation %s: %q does not appear to be a valid MagicDNS name", AnnotationTailnetTargetFQDN, fqdn))
 		}
 	}
-
-	// TODO(irbekrm): validate that tailscale.com/tailnet-ip annotation is a
-	// valid IP address (tailscale/tailscale#13671).
+	if ipStr := svc.Annotations[AnnotationTailnetTargetIP]; ipStr != "" {
+		ip, err := netip.ParseAddr(ipStr)
+		if err != nil {
+			violations = append(violations, fmt.Sprintf("invalid value of annotation %s: %q could not be parsed as a valid IP Address, error: %s", AnnotationTailnetTargetIP, ipStr, err))
+		} else if !ip.IsValid() {
+			violations = append(violations, fmt.Sprintf("parsed IP address in annotation %s: %q is not valid", AnnotationTailnetTargetIP, ipStr))
+		}
+	}
 
 	svcName := nameForService(svc)
 	if err := dnsname.ValidLabel(svcName); err != nil {