diff --git a/internal/admission/admit_nodepool.go b/internal/admission/admit_nodepool.go
index bc6069ed8c9..f2cd5b78875 100644
--- a/internal/admission/admit_nodepool.go
+++ b/internal/admission/admit_nodepool.go
@@ -92,6 +92,11 @@ func mutateNodePoolServiceProviderProperties(ctx context.Context, admissionConte
 	errs = append(errs, mutateNodePoolExperimentalTags(ctx, admissionContext, op)...)
 	errs = append(errs, mutateNodePoolCreateOperationCompletionDeadline(ctx, admissionContext, op, fldPath.Child("createOperationCompletionDeadline"), &newObj.CreateOperationCompletionDeadline)...)
 
+	if op.Type == operation.Create {
+		subscription := admissionContext.Subscription
+		newObj.ExperimentalFeaturesEnabled = subscription != nil && subscription.HasRegisteredFeature(metadataapi.FeatureExperimentalReleaseFeatures)
+	}
+
 	return errs
 }
 
diff --git a/internal/admission/admit_nodepool_test.go b/internal/admission/admit_nodepool_test.go
index d44dcce0d32..fe845fe7923 100644
--- a/internal/admission/admit_nodepool_test.go
+++ b/internal/admission/admit_nodepool_test.go
@@ -347,6 +347,68 @@ func TestMutateNodePoolCreateOperationCompletionDeadline(t *testing.T) {
 	}
 }
 
+func TestMutateNodePoolExperimentalFeaturesEnabled(t *testing.T) {
+	afecRegistered := &coreapi.Subscription{
+		Properties: &coreapi.SubscriptionProperties{
+			RegisteredFeatures: &[]coreapi.Feature{
+				{
+					Name:  ptr.To(metadataapi.FeatureExperimentalReleaseFeatures),
+					State: ptr.To("Registered"),
+				},
+			},
+		},
+	}
+
+	tests := []struct {
+		name         string
+		op           operation.Type
+		subscription *coreapi.Subscription
+		expected     bool
+	}{
+		{
+			name:         "create: AFEC registered sets ExperimentalFeaturesEnabled=true",
+			op:           operation.Create,
+			subscription: afecRegistered,
+			expected:     true,
+		},
+		{
+			name:         "create: no AFEC leaves ExperimentalFeaturesEnabled=false",
+			op:           operation.Create,
+			subscription: &coreapi.Subscription{Properties: &coreapi.SubscriptionProperties{}},
+			expected:     false,
+		},
+		{
+			name:         "create: nil subscription leaves ExperimentalFeaturesEnabled=false",
+			op:           operation.Create,
+			subscription: nil,
+			expected:     false,
+		},
+		{
+			name:         "update: AFEC registered does not set ExperimentalFeaturesEnabled",
+			op:           operation.Update,
+			subscription: afecRegistered,
+			expected:     false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			nodePool := &coreapi.HCPOpenShiftClusterNodePool{}
+			admissionContext := &NodePoolAdmissionContext{
+				Clock:        utilsclock.RealClock{},
+				Subscription: tt.subscription,
+				Cluster:      &coreapi.HCPOpenShiftCluster{},
+			}
+			if tt.op == operation.Update {
+				admissionContext.OriginalNodePool = &coreapi.HCPOpenShiftClusterNodePool{}
+			}
+			errs := MutateNodePool(context.Background(), admissionContext, operation.Operation{Type: tt.op}, nodePool, admissionContext.OriginalNodePool)
+			require.Empty(t, errs)
+			assert.Equal(t, tt.expected, nodePool.ServiceProviderProperties.ExperimentalFeaturesEnabled)
+		})
+	}
+}
+
 func TestAdmitNodePool_SubnetVNet(t *testing.T) {
 	const (
 		clusterSubnet       = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/rg/providers/Microsoft.Network/virtualNetworks/cluster-vnet/subnets/cluster-subnet"
diff --git a/internal/api/coreapi/types_nodepool.go b/internal/api/coreapi/types_nodepool.go
index 7234b8c0c8e..4f3cdde797a 100644
--- a/internal/api/coreapi/types_nodepool.go
+++ b/internal/api/coreapi/types_nodepool.go
@@ -124,6 +124,13 @@ type HCPOpenShiftClusterNodePoolServiceProviderProperties struct {
 	// The operation node pool create controller uses this value to decide about marking the install as failed.
 	// The e2e tests set this value to one minute less than the default timeout.
 	CreateOperationCompletionDeadline *metav1.Time `json:"createOperationCompletionDeadline,omitempty"`
+
+	// ExperimentalFeaturesEnabled records whether the FeatureExperimentalReleaseFeatures AFEC was
+	// registered on the subscription at node pool creation time. Used by internal/ocm/convert.go
+	// to gate experimental CS fields (e.g. SseEncryptionSetResourceId on the OS disk) that are
+	// only sent to Cluster Service when the AFEC is registered.
+	// Written by: Frontend PUT NodePool (Create)
+	ExperimentalFeaturesEnabled bool `json:"experimentalFeaturesEnabled,omitempty"`
 }
 
 // NodePoolVersionProfile represents the worker node pool version.
diff --git a/internal/apitesting/coreapitesting/fuzz.go b/internal/apitesting/coreapitesting/fuzz.go
index d3ff1714233..85bdb5e73fa 100644
--- a/internal/apitesting/coreapitesting/fuzz.go
+++ b/internal/apitesting/coreapitesting/fuzz.go
@@ -196,6 +196,7 @@ func CommonRoundTripFuzzFuncs() []interface{} {
 			j.ActiveOperationID = ""
 			j.ClusterServiceID = nil
 			j.UsesNewNodePoolDeletionApproach = false
+			j.ExperimentalFeaturesEnabled = false
 		},
 		func(j *coreapi.HCPOpenShiftClusterExternalAuthServiceProviderProperties, c randfill.Continue) {
 			c.FillNoCustom(j)
diff --git a/internal/ocm/convert.go b/internal/ocm/convert.go
index 9b63f26c7c1..822914830b5 100644
--- a/internal/ocm/convert.go
+++ b/internal/ocm/convert.go
@@ -224,6 +224,17 @@ func convertEnableEncryptionAtHostToCSBuilder(in coreapi.NodePoolPlatformProfile
 	return arohcpv1alpha1.NewAzureNodePoolEncryptionAtHost().State(state)
 }
 
+func buildCSOsDisk(osDisk coreapi.OSDiskProfile, storageAccountType, persistence string, experimentalFeaturesEnabled bool) *arohcpv1alpha1.AzureNodePoolOsDiskBuilder {
+	builder := arohcpv1alpha1.NewAzureNodePoolOsDisk().
+		SizeGibibytes(int(*osDisk.SizeGiB)).
+		StorageAccountType(storageAccountType).
+		Persistence(persistence)
+	if experimentalFeaturesEnabled && osDisk.EncryptionSetID != nil {
+		builder.SseEncryptionSetResourceId(osDisk.EncryptionSetID.String())
+	}
+	return builder
+}
+
 func convertClusterImageRegistryStateRPToCS(in coreapi.ClusterImageRegistryProfile) (string, error) {
 	switch in.State {
 	case metadataapi.ClusterImageRegistryStateDisabled:
@@ -629,10 +640,7 @@ func BuildCSNodePool(ctx context.Context, nodePool *coreapi.HCPOpenShiftClusterN
 				ResourceName(strings.ToLower(nodePool.Name)).
 				VMSize(nodePool.Properties.Platform.VMSize).
 				EncryptionAtHost(convertEnableEncryptionAtHostToCSBuilder(nodePool.Properties.Platform)).
-				OsDisk(arohcpv1alpha1.NewAzureNodePoolOsDisk().
-					SizeGibibytes(int(*nodePool.Properties.Platform.OSDisk.SizeGiB)).
-					StorageAccountType(csDiskStorageAccountType).
-					Persistence(csPersistence))).
+				OsDisk(buildCSOsDisk(nodePool.Properties.Platform.OSDisk, csDiskStorageAccountType, csPersistence, nodePool.ServiceProviderProperties.ExperimentalFeaturesEnabled))).
 			AvailabilityZone(nodePool.Properties.Platform.AvailabilityZone).
 			AutoRepair(nodePool.Properties.AutoRepair)
 	}
diff --git a/internal/ocm/convert_test.go b/internal/ocm/convert_test.go
index b5aae7fffc2..669adb315d4 100644
--- a/internal/ocm/convert_test.go
+++ b/internal/ocm/convert_test.go
@@ -440,6 +440,46 @@ func TestBuildCSNodePool(t *testing.T) {
 					),
 				),
 		},
+		{
+			name: "passes disk encryption set ID to CS when AFEC is enabled",
+			hcpNodePool: getHCPNodePoolResource(
+				func(hsc *coreapi.HCPOpenShiftClusterNodePool) {
+					hsc.Properties.Platform.OSDisk.EncryptionSetID = metadataapi.Must(azcorearm.ParseResourceID(
+						"/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/test-rg/providers/Microsoft.Compute/diskEncryptionSets/test-des"))
+					hsc.ServiceProviderProperties.ExperimentalFeaturesEnabled = true
+				},
+			),
+			expectedCSNodePool: getBaseCSNodePoolBuilder().
+				AzureNodePool(arohcpv1alpha1.NewAzureNodePool().
+					ResourceName("").
+					VMSize("").
+					EncryptionAtHost(
+						arohcpv1alpha1.NewAzureNodePoolEncryptionAtHost().
+							State(csEncryptionAtHostStateDisabled),
+					).
+					OsDisk(arohcpv1alpha1.NewAzureNodePoolOsDisk().
+						SizeGibibytes(64).
+						StorageAccountType(string(metadataapi.DiskStorageAccountTypePremium_LRS)).
+						Persistence("persistent").
+						SseEncryptionSetResourceId("/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/test-rg/providers/Microsoft.Compute/diskEncryptionSets/test-des"),
+					),
+				),
+		},
+		{
+			name: "disk encryption set ID not passed to CS when AFEC is disabled",
+			hcpNodePool: getHCPNodePoolResource(
+				func(hsc *coreapi.HCPOpenShiftClusterNodePool) {
+					hsc.Properties.Platform.OSDisk.EncryptionSetID = metadataapi.Must(azcorearm.ParseResourceID(
+						"/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/test-rg/providers/Microsoft.Compute/diskEncryptionSets/test-des"))
+				},
+			),
+			expectedCSNodePool: getBaseCSNodePoolBuilder(),
+		},
+		{
+			name:               "nil disk encryption set ID does not set SSE field",
+			hcpNodePool:        getHCPNodePoolResource(),
+			expectedCSNodePool: getBaseCSNodePoolBuilder(),
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {