diff --git a/manifests/ate-install/generated/ate.dev_actortemplates.yaml b/manifests/ate-install/generated/ate.dev_actortemplates.yaml
index 0c8af4b08..0bebc1473 100644
--- a/manifests/ate-install/generated/ate.dev_actortemplates.yaml
+++ b/manifests/ate-install/generated/ate.dev_actortemplates.yaml
@@ -428,6 +428,11 @@ spec:
               rule: '!has(self.containers) || self.containers.all(c, !has(c.volumeMounts)
                 || c.volumeMounts.filter(vm, has(self.volumes) && self.volumes.exists(v,
                 v.name == vm.name && has(v.durableDir))).size() <= 1)'
+            - message: All volumes defined in spec.volumes must be mounted by at least
+                one container
+              rule: '!has(self.volumes) || self.volumes.all(v, has(self.containers)
+                && self.containers.exists(c, has(c.volumeMounts) && c.volumeMounts.exists(vm,
+                vm.name == v.name)))'
             - message: DurableDir volumes are not supported when sandboxClass is 'microvm'
               rule: '!has(self.sandboxClass) || self.sandboxClass != ''microvm'' ||
                 !has(self.volumes) || !self.volumes.exists(v, has(v.durableDir))'
diff --git a/pkg/api/v1alpha1/actortemplate_types.go b/pkg/api/v1alpha1/actortemplate_types.go
index eefb824b0..c6933c104 100644
--- a/pkg/api/v1alpha1/actortemplate_types.go
+++ b/pkg/api/v1alpha1/actortemplate_types.go
@@ -296,6 +296,7 @@ type SnapshotsConfig struct {
 //
 // +kubebuilder:validation:XValidation:rule="!has(self.volumes) || self.volumes.filter(v, has(v.durableDir)).size() <= 1",message="At most one DurableDir-typed volume is supported per ActorTemplate"
 // +kubebuilder:validation:XValidation:rule="!has(self.containers) || self.containers.all(c, !has(c.volumeMounts) || c.volumeMounts.filter(vm, has(self.volumes) && self.volumes.exists(v, v.name == vm.name && has(v.durableDir))).size() <= 1)",message="A container may mount at most one DurableDir-typed volume"
+// +kubebuilder:validation:XValidation:rule="!has(self.volumes) || self.volumes.all(v, has(self.containers) && self.containers.exists(c, has(c.volumeMounts) && c.volumeMounts.exists(vm, vm.name == v.name)))",message="All volumes defined in spec.volumes must be mounted by at least one container"
 // +kubebuilder:validation:XValidation:rule="!has(self.sandboxClass) || self.sandboxClass != 'microvm' || !has(self.volumes) || !self.volumes.exists(v, has(v.durableDir))",message="DurableDir volumes are not supported when sandboxClass is 'microvm'"
 // +kubebuilder:validation:XValidation:rule="!has(self.sandboxClass) || self.sandboxClass != 'microvm' || !has(self.volumes) || !self.volumes.exists(v, has(v.externalVolumeTemplate))",message="ExternalVolumes are not supported when sandboxClass is 'microvm'"
 type ActorTemplateSpec struct {
diff --git a/pkg/api/v1alpha1/actortemplate_validation_test.go b/pkg/api/v1alpha1/actortemplate_validation_test.go
index 6066ea948..89ccbc923 100644
--- a/pkg/api/v1alpha1/actortemplate_validation_test.go
+++ b/pkg/api/v1alpha1/actortemplate_validation_test.go
@@ -1069,6 +1069,44 @@ func TestActorTemplateValidation(t *testing.T) {
 			at.Spec.SandboxClass = SandboxClassMicroVM
 		},
 		wantErr: false,
+	}, {
+		name: "Volumes: volume without volumeMount is invalid",
+		mutate: func(at *ActorTemplate) {
+			at.Spec.Volumes = []Volume{
+				{Name: "vol1", VolumeSource: VolumeSource{DurableDir: &DurableDirVolumeSource{}}},
+			}
+		},
+		wantErr: true,
+		errMsg:  "All volumes defined in spec.volumes must be mounted by at least one container",
+	}, {
+		name: "Volumes: multiple volumes with one unmounted is invalid",
+		mutate: func(at *ActorTemplate) {
+			at.Spec.Volumes = []Volume{
+				{
+					Name: "vol1",
+					VolumeSource: VolumeSource{
+						ExternalVolumeTemplate: &ExternalVolumeTemplate{
+							Capacity:         resource.MustParse("10Gi"),
+							StorageClassName: "standard",
+						},
+					},
+				},
+				{
+					Name: "vol2",
+					VolumeSource: VolumeSource{
+						ExternalVolumeTemplate: &ExternalVolumeTemplate{
+							Capacity:         resource.MustParse("20Gi"),
+							StorageClassName: "pd-ssd",
+						},
+					},
+				},
+			}
+			at.Spec.Containers[0].VolumeMounts = []VolumeMount{
+				{Name: "vol1", MountPath: "/mnt/vol1"},
+			}
+		},
+		wantErr: true,
+		errMsg:  "All volumes defined in spec.volumes must be mounted by at least one container",
 	}}
 
 	for _, tt := range tests {