diff --git a/azurerm/internal/services/web/function_app.go b/azurerm/internal/services/web/function_app.go
index 61c96562ce96..7c28886b136e 100644
--- a/azurerm/internal/services/web/function_app.go
+++ b/azurerm/internal/services/web/function_app.go
@@ -69,6 +69,7 @@ func schemaAppServiceFunctionAppSiteConfig() *schema.Schema {
 				"pre_warmed_instance_count": {
 					Type:         schema.TypeInt,
 					Optional:     true,
+					Computed:     true,
 					ValidateFunc: validation.IntBetween(0, 10),
 				},
 
diff --git a/azurerm/internal/services/web/function_app_resource_test.go b/azurerm/internal/services/web/function_app_resource_test.go
index 8be6e78faf8c..b014f2196306 100644
--- a/azurerm/internal/services/web/function_app_resource_test.go
+++ b/azurerm/internal/services/web/function_app_resource_test.go
@@ -651,6 +651,22 @@ func TestAccFunctionApp_preWarmedInstanceCount(t *testing.T) {
 	})
 }
 
+func TestAccAzureRMFunctionApp_computedPreWarmedInstanceCount(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_function_app", "test")
+	r := FunctionAppResource{}
+
+	data.ResourceTest(t, r, []resource.TestStep{
+		{
+			Config: r.computedPreWarmedInstanceCount(data),
+			Check: resource.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("site_config.0.pre_warmed_instance_count").HasValue("1"),
+			),
+		},
+		data.ImportStep(),
+	})
+}
+
 func TestAccFunctionApp_oneIpRestriction(t *testing.T) {
 	data := acceptance.BuildTestData(t, "azurerm_function_app", "test")
 	r := FunctionAppResource{}
@@ -2303,6 +2319,47 @@ resource "azurerm_function_app" "test" {
 `, data.RandomInteger, data.Locations.Primary, data.RandomString, data.RandomInteger, data.RandomInteger)
 }
 
+func (r FunctionAppResource) computedPreWarmedInstanceCount(data acceptance.TestData) string {
+	return fmt.Sprintf(`
+provider "azurerm" {
+  features {}
+}
+
+resource "azurerm_resource_group" "test" {
+  name     = "acctestRG-%d"
+  location = "%s"
+}
+
+resource "azurerm_storage_account" "test" {
+  name                     = "acctestsa%s"
+  resource_group_name      = azurerm_resource_group.test.name
+  location                 = azurerm_resource_group.test.location
+  account_tier             = "Standard"
+  account_replication_type = "LRS"
+}
+
+resource "azurerm_app_service_plan" "test" {
+  name                = "acctestASP-%d"
+  resource_group_name = azurerm_resource_group.test.name
+  location            = azurerm_resource_group.test.location
+  kind                = "elastic"
+
+  sku {
+    tier = "ElasticPremium"
+    size = "EP1"
+  }
+}
+
+resource "azurerm_function_app" "test" {
+  name                      = "acctest-%d-func"
+  location                  = azurerm_resource_group.test.location
+  resource_group_name       = azurerm_resource_group.test.name
+  app_service_plan_id       = azurerm_app_service_plan.test.id
+  storage_connection_string = azurerm_storage_account.test.primary_connection_string
+}
+`, data.RandomInteger, data.Locations.Primary, data.RandomString, data.RandomInteger, data.RandomInteger)
+}
+
 func (r FunctionAppResource) oneIpRestriction(data acceptance.TestData) string {
 	return fmt.Sprintf(`
 provider "azurerm" {