diff --git a/internal/services/appservice/helpers/function_app_schema.go b/internal/services/appservice/helpers/function_app_schema.go
index 43b3388ae6cc..83e711de146e 100644
--- a/internal/services/appservice/helpers/function_app_schema.go
+++ b/internal/services/appservice/helpers/function_app_schema.go
@@ -1061,6 +1061,7 @@ func linuxFunctionAppStackSchema() *pluginsdk.Schema {
 					ValidateFunc: validation.StringInSlice([]string{
 						"12",
 						"14",
+						"16", // preview LTS Support
 					}, false),
 					ExactlyOneOf: []string{
 						"site_config.0.application_stack.0.dotnet_version",
@@ -1284,8 +1285,9 @@ func windowsFunctionAppStackSchema() *pluginsdk.Schema {
 					Type:     pluginsdk.TypeString,
 					Optional: true,
 					ValidateFunc: validation.StringInSlice([]string{
-						"12",
-						"14",
+						"~12",
+						"~14",
+						"~16",
 					}, false),
 					ExactlyOneOf: []string{
 						"site_config.0.application_stack.0.dotnet_version",
diff --git a/internal/services/appservice/linux_function_app_resource_test.go b/internal/services/appservice/linux_function_app_resource_test.go
index 5feaf9cc1b55..becfe5a5947b 100644
--- a/internal/services/appservice/linux_function_app_resource_test.go
+++ b/internal/services/appservice/linux_function_app_resource_test.go
@@ -671,7 +671,7 @@ func TestAccLinuxFunctionApp_appStackNode(t *testing.T) {
 
 	data.ResourceTest(t, r, []acceptance.TestStep{
 		{
-			Config: r.appStackNode(data, SkuBasicPlan, "14"),
+			Config: r.appStackNode(data, SkuConsumptionPlan, "14"),
 			Check: acceptance.ComposeTestCheckFunc(
 				check.That(data.ResourceName).ExistsInAzure(r),
 				check.That(data.ResourceName).Key("kind").HasValue("functionapp,linux"),
@@ -694,6 +694,14 @@ func TestAccLinuxFunctionApp_appStackNodeUpdate(t *testing.T) {
 			),
 		},
 		data.ImportStep(),
+		{
+			Config: r.appStackNode(data, SkuBasicPlan, "16"),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("kind").HasValue("functionapp,linux"),
+			),
+		},
+		data.ImportStep(),
 		{
 			Config: r.appStackNode(data, SkuBasicPlan, "14"),
 			Check: acceptance.ComposeTestCheckFunc(
diff --git a/internal/services/appservice/windows_function_app_resource_test.go b/internal/services/appservice/windows_function_app_resource_test.go
index e54f7602b127..a049f87b7049 100644
--- a/internal/services/appservice/windows_function_app_resource_test.go
+++ b/internal/services/appservice/windows_function_app_resource_test.go
@@ -673,7 +673,7 @@ func TestAccWindowsFunctionApp_appStackNode(t *testing.T) {
 
 	data.ResourceTest(t, r, []acceptance.TestStep{
 		{
-			Config: r.appStackNode(data, SkuBasicPlan, "14"),
+			Config: r.appStackNode(data, SkuConsumptionPlan, "~14"),
 			Check: acceptance.ComposeTestCheckFunc(
 				check.That(data.ResourceName).ExistsInAzure(r),
 				check.That(data.ResourceName).Key("kind").HasValue("functionapp"),
@@ -689,7 +689,7 @@ func TestAccWindowsFunctionApp_appStackNodeUpdate(t *testing.T) {
 
 	data.ResourceTest(t, r, []acceptance.TestStep{
 		{
-			Config: r.appStackNode(data, SkuBasicPlan, "12"),
+			Config: r.appStackNode(data, SkuBasicPlan, "~12"),
 			Check: acceptance.ComposeTestCheckFunc(
 				check.That(data.ResourceName).ExistsInAzure(r),
 				check.That(data.ResourceName).Key("kind").HasValue("functionapp"),
@@ -697,7 +697,15 @@ func TestAccWindowsFunctionApp_appStackNodeUpdate(t *testing.T) {
 		},
 		data.ImportStep(),
 		{
-			Config: r.appStackNode(data, SkuBasicPlan, "14"),
+			Config: r.appStackNode(data, SkuBasicPlan, "~16"),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("kind").HasValue("functionapp"),
+			),
+		},
+		data.ImportStep(),
+		{
+			Config: r.appStackNode(data, SkuBasicPlan, "~14"),
 			Check: acceptance.ComposeTestCheckFunc(
 				check.That(data.ResourceName).ExistsInAzure(r),
 				check.That(data.ResourceName).Key("kind").HasValue("functionapp"),
diff --git a/website/docs/r/linux_function_app.html.markdown b/website/docs/r/linux_function_app.html.markdown
index 48b1450855c3..1c9c8d4643c6 100644
--- a/website/docs/r/linux_function_app.html.markdown
+++ b/website/docs/r/linux_function_app.html.markdown
@@ -136,7 +136,7 @@ A `application_stack` block supports the following:
 
 * `java_version` - (Optional) The Version of Java to use. Supported versions include `8`, and `11`.
 
-* `node_version` - (Optional) The version of Node to run. Possible values include `12`, and `14`.
+* `node_version` - (Optional) The version of Node to run. Possible values include `12`, `14`, and `16`.
 
 * `python_version` - (Optional) The version of Python to run. Possible values include `3.6`, `3.7`, `3.8`, and `3.9`.
 
diff --git a/website/docs/r/windows_function_app.html.markdown b/website/docs/r/windows_function_app.html.markdown
index 67338d094110..dba2b12cbfe7 100644
--- a/website/docs/r/windows_function_app.html.markdown
+++ b/website/docs/r/windows_function_app.html.markdown
@@ -134,7 +134,7 @@ A `application_stack` block supports the following:
 
 * `java_version` - (Optional) The Version of Java to use. Supported versions include `8`, and `11`.
 
-* `node_version` - (Optional) The version of Node to run. Possible values include `12`, and `14`.
+* `node_version` - (Optional) The version of Node to run. Possible values include `~12`, `~14`, and `~16`.
 
 * `powershell_core_version` - (Optional) The version of PowerShell Core to run. Possible values are `7`.