diff --git a/.changelog/18635.txt b/.changelog/18635.txt
new file mode 100644
index 000000000000..4bc2b1d8b138
--- /dev/null
+++ b/.changelog/18635.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_elasticache_replication_group: Remmoves incorrect plan-time validation for `automatic_failover_enabled`
+```
diff --git a/aws/resource_aws_elasticache_replication_group.go b/aws/resource_aws_elasticache_replication_group.go
index ae54362f0023..774cf4b7542f 100644
--- a/aws/resource_aws_elasticache_replication_group.go
+++ b/aws/resource_aws_elasticache_replication_group.go
@@ -301,27 +301,6 @@ func resourceAwsElasticacheReplicationGroup() *schema.Resource {
 				}
 				return nil
 			},
-			func(_ context.Context, diff *schema.ResourceDiff, v interface{}) error {
-				if v := diff.Get("automatic_failover_enabled").(bool); !v {
-					return nil
-				}
-
-				if v, ok := diff.GetOkExists("number_cache_clusters"); ok {
-					if v.(int) > 1 {
-						return nil
-					}
-					return errors.New(`if automatic_failover_enabled is true, number_cache_clusters must be greater than 1`)
-				}
-
-				if v, ok := diff.GetOkExists("cluster_mode.0.replicas_per_node_group"); ok {
-					if v.(int) > 0 {
-						return nil
-					}
-					return errors.New(`if automatic_failover_enabled is true, cluster_mode[0].replicas_per_node_group must be greater than 0`)
-				}
-
-				return nil
-			},
 			customdiff.ComputedIf("member_clusters", func(ctx context.Context, diff *schema.ResourceDiff, meta interface{}) bool {
 				return diff.HasChange("number_cache_clusters") ||
 					diff.HasChange("cluster_mode.0.num_node_groups") ||
diff --git a/aws/resource_aws_elasticache_replication_group_test.go b/aws/resource_aws_elasticache_replication_group_test.go
index 539c62faaa65..76a74b87f20f 100644
--- a/aws/resource_aws_elasticache_replication_group_test.go
+++ b/aws/resource_aws_elasticache_replication_group_test.go
@@ -433,7 +433,7 @@ func TestAccAWSElasticacheReplicationGroup_multiAzInVpc(t *testing.T) {
 	})
 }
 
-func TestAccAWSElasticacheReplicationGroup_multiAz_NoAutomaticFailover(t *testing.T) {
+func TestAccAWSElasticacheReplicationGroup_Validation_multiAz_NoAutomaticFailover(t *testing.T) {
 	rName := acctest.RandomWithPrefix("tf-acc-test")
 
 	resource.ParallelTest(t, resource.TestCase{
@@ -450,27 +450,6 @@ func TestAccAWSElasticacheReplicationGroup_multiAz_NoAutomaticFailover(t *testin
 	})
 }
 
-func TestAccAWSElasticacheReplicationGroup_AutomaticFailover_OneCacheCluster(t *testing.T) {
-	rName := acctest.RandomWithPrefix("tf-acc-test")
-
-	resource.ParallelTest(t, resource.TestCase{
-		PreCheck:     func() { testAccPreCheck(t) },
-		ErrorCheck:   testAccErrorCheck(t, elasticache.EndpointsID),
-		Providers:    testAccProviders,
-		CheckDestroy: testAccCheckAWSElasticacheReplicationDestroy,
-		Steps: []resource.TestStep{
-			{
-				Config:      testAccAWSElasticacheReplicationGroupConfig_MultiAZOneCacheCluster_SingleNodeGroup(rName),
-				ExpectError: regexp.MustCompile(`if automatic_failover_enabled is true, number_cache_clusters must be greater than 1`),
-			},
-			{
-				Config:      testAccAWSElasticacheReplicationGroupConfig_MultiAZOneCacheCluster_ClusterMode(rName),
-				ExpectError: regexp.MustCompile(`if automatic_failover_enabled is true, cluster_mode\[0\].replicas_per_node_group must be greater than 0`),
-			},
-		},
-	})
-}
-
 func TestAccAWSElasticacheReplicationGroup_redisClusterInVpc2(t *testing.T) {
 	var rg elasticache.ReplicationGroup
 	rName := acctest.RandomWithPrefix("tf-acc-test")
@@ -798,6 +777,42 @@ func TestAccAWSElasticacheReplicationGroup_ClusterMode_UpdateNumNodeGroupsAndRep
 	})
 }
 
+func TestAccAWSElasticacheReplicationGroup_ClusterMode_SingleNode(t *testing.T) {
+	var rg elasticache.ReplicationGroup
+	rName := acctest.RandomWithPrefix("tf-acc-test")
+	resourceName := "aws_elasticache_replication_group.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		ErrorCheck:   testAccErrorCheck(t, elasticache.EndpointsID),
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSElasticacheReplicationDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSElasticacheReplicationGroupNativeRedisClusterConfig_SingleNode(rName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSElasticacheReplicationGroupExists(resourceName, &rg),
+					resource.TestCheckResourceAttr(resourceName, "cluster_enabled", "true"),
+					resource.TestCheckResourceAttr(resourceName, "parameter_group_name", "default.redis6.x.cluster.on"),
+					resource.TestCheckResourceAttr(resourceName, "cluster_mode.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "cluster_mode.0.num_node_groups", "1"),
+					resource.TestCheckResourceAttr(resourceName, "cluster_mode.0.replicas_per_node_group", "0"),
+					resource.TestCheckResourceAttr(resourceName, "multi_az_enabled", "false"),
+					resource.TestCheckResourceAttr(resourceName, "automatic_failover_enabled", "true"),
+					resource.TestCheckResourceAttr(resourceName, "number_cache_clusters", "1"),
+					resource.TestCheckResourceAttr(resourceName, "member_clusters.#", "1"),
+				),
+			},
+			{
+				ResourceName:            resourceName,
+				ImportState:             true,
+				ImportStateVerify:       true,
+				ImportStateVerifyIgnore: []string{"apply_immediately"},
+			},
+		},
+	})
+}
+
 func TestAccAWSElasticacheReplicationGroup_clusteringAndCacheNodesCausesError(t *testing.T) {
 	rInt := acctest.RandInt()
 	rName := acctest.RandomWithPrefix("tf-acc-test")
@@ -1930,36 +1945,6 @@ resource "aws_elasticache_replication_group" "test" {
 `, rName)
 }
 
-func testAccAWSElasticacheReplicationGroupConfig_MultiAZOneCacheCluster_SingleNodeGroup(rName string) string {
-	return fmt.Sprintf(`
-resource "aws_elasticache_replication_group" "test" {
-  replication_group_id          = %[1]q
-  replication_group_description = "test description"
-  number_cache_clusters         = 1
-  node_type                     = "cache.t3.small"
-  automatic_failover_enabled    = true
-  multi_az_enabled              = true
-}
-`, rName)
-}
-
-func testAccAWSElasticacheReplicationGroupConfig_MultiAZOneCacheCluster_ClusterMode(rName string) string {
-	return fmt.Sprintf(`
-resource "aws_elasticache_replication_group" "test" {
-  replication_group_id          = %[1]q
-  replication_group_description = "test description"
-  node_type                     = "cache.t3.small"
-  automatic_failover_enabled    = true
-  multi_az_enabled              = true
-
-  cluster_mode {
-    num_node_groups         = 1
-    replicas_per_node_group = 0
-  }
-}
-`, rName)
-}
-
 func testAccAWSElasticacheReplicationGroupRedisClusterInVPCConfig(rName string) string {
 	return fmt.Sprintf(`
 data "aws_availability_zones" "available" {
@@ -2218,6 +2203,25 @@ resource "aws_elasticache_replication_group" "test" {
 `, rName))
 }
 
+func testAccAWSElasticacheReplicationGroupNativeRedisClusterConfig_SingleNode(rName string) string {
+	return composeConfig(
+		testAccAvailableAZsNoOptInConfig(),
+		fmt.Sprintf(`
+resource "aws_elasticache_replication_group" "test" {
+  replication_group_id          = %[1]q
+  replication_group_description = "test description"
+  node_type                     = "cache.t2.medium"
+  automatic_failover_enabled    = true
+
+  parameter_group_name = "default.redis6.x.cluster.on"
+  cluster_mode {
+    num_node_groups         = 1
+    replicas_per_node_group = 0
+  }
+}
+`, rName))
+}
+
 func testAccAWSElasticacheReplicationGroup_UseCmkKmsKeyId(rInt int, rString string) string {
 	return fmt.Sprintf(`
 data "aws_availability_zones" "available" {