diff --git a/.changelog/30379.txt b/.changelog/30379.txt
new file mode 100644
index 000000000000..687b1456b9ca
--- /dev/null
+++ b/.changelog/30379.txt
@@ -0,0 +1,7 @@
+```release-note:bug
+resource/aws_rds_cluster: Fix crash when updating `master_password`
+```
+
+```release-note:bug
+resource/aws_db_instance: Fix crash when updating `password`
+```
\ No newline at end of file
diff --git a/internal/service/rds/cluster.go b/internal/service/rds/cluster.go
index a147b8ff8d74..f0d971fa89e4 100644
--- a/internal/service/rds/cluster.go
+++ b/internal/service/rds/cluster.go
@@ -1279,12 +1279,12 @@ func resourceClusterUpdate(ctx context.Context, d *schema.ResourceData, meta int
 			input.ManageMasterUserPassword = aws.Bool(d.Get("manage_master_user_password").(bool))
 		}
 		if d.HasChange("master_password") {
-			if v, ok := d.GetOk("master_password"); ok && len(v.([]interface{})) > 0 && v.([]interface{}) != nil {
+			if v, ok := d.GetOk("master_password"); ok {
 				input.MasterUserPassword = aws.String(v.(string))
 			}
 		}
 		if d.HasChange("master_user_secret_kms_key_id") {
-			if v, ok := d.GetOk("master_user_secret_kms_key_id"); ok && len(v.([]interface{})) > 0 && v.([]interface{}) != nil {
+			if v, ok := d.GetOk("master_user_secret_kms_key_id"); ok {
 				input.MasterUserSecretKmsKeyId = aws.String(v.(string))
 			}
 		}
diff --git a/internal/service/rds/cluster_test.go b/internal/service/rds/cluster_test.go
index 37d0d5d44498..3cd4435a953d 100644
--- a/internal/service/rds/cluster_test.go
+++ b/internal/service/rds/cluster_test.go
@@ -2338,6 +2338,36 @@ func TestAccRDSCluster_enableHTTPEndpoint(t *testing.T) {
 	})
 }
 
+func TestAccRDSCluster_password(t *testing.T) {
+	ctx := acctest.Context(t)
+	var dbCluster rds.DBCluster
+	rName := sdkacctest.RandomWithPrefix(acctest.ResourcePrefix)
+	resourceName := "aws_rds_cluster.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:                 func() { acctest.PreCheck(ctx, t) },
+		ErrorCheck:               acctest.ErrorCheck(t, rds.EndpointsID),
+		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories,
+		CheckDestroy:             testAccCheckClusterDestroy(ctx),
+		Steps: []resource.TestStep{
+			{
+				Config: testAccClusterConfig_password(rName, "valid-password-1"),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckClusterExists(ctx, resourceName, &dbCluster),
+					resource.TestCheckResourceAttr(resourceName, "master_password", "valid-password-1"),
+				),
+			},
+			{
+				Config: testAccClusterConfig_password(rName, "valid-password-2"),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckClusterExists(ctx, resourceName, &dbCluster),
+					resource.TestCheckResourceAttr(resourceName, "master_password", "valid-password-2"),
+				),
+			},
+		},
+	})
+}
+
 func testAccCheckClusterDestroy(ctx context.Context) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		return testAccCheckClusterDestroyWithProvider(ctx)(s, acctest.Provider)
@@ -2470,7 +2500,8 @@ resource "aws_rds_cluster" "test" {
   database_name                   = "test"
   manage_master_user_password     = true
   master_username                 = "tfacctest"
-  db_cluster_parameter_group_name = "default.aurora5.6"
+  engine                          = "aurora-mysql"
+  db_cluster_parameter_group_name = "default.aurora-mysql5.7"
   skip_final_snapshot             = true
 }
 `, rName)
@@ -4359,3 +4390,17 @@ resource "aws_rds_cluster" "test" {
 }
 `, rName, enableHttpEndpoint)
 }
+
+func testAccClusterConfig_password(rName, password string) string {
+	return fmt.Sprintf(`
+resource "aws_rds_cluster" "test" {
+  cluster_identifier              = %[1]q
+  database_name                   = "test"
+  master_username                 = "tfacctest"
+  master_password                 = %[2]q
+  engine                          = "aurora-mysql"
+  db_cluster_parameter_group_name = "default.aurora-mysql5.7"
+  skip_final_snapshot             = true
+}
+`, rName, password)
+}
diff --git a/internal/service/rds/instance.go b/internal/service/rds/instance.go
index 9e8182a17239..d6f0b7329504 100644
--- a/internal/service/rds/instance.go
+++ b/internal/service/rds/instance.go
@@ -2092,8 +2092,11 @@ func dbInstancePopulateModify(input *rds_sdkv2.ModifyDBInstanceInput, d *schema.
 	}
 
 	if d.HasChange("master_user_secret_kms_key_id") {
-		if v, ok := d.GetOk("master_user_secret_kms_key_id"); ok && len(v.([]interface{})) > 0 && v.([]interface{}) != nil {
+		needsModify = true
+		if v, ok := d.GetOk("master_user_secret_kms_key_id"); ok {
 			input.MasterUserSecretKmsKeyId = aws.String(v.(string))
+			// InvalidParameterValue: A ManageMasterUserPassword value is required when MasterUserSecretKmsKeyId is specified.
+			input.ManageMasterUserPassword = aws.Bool(d.Get("manage_master_user_password").(bool))
 		}
 	}
 
@@ -2139,7 +2142,7 @@ func dbInstancePopulateModify(input *rds_sdkv2.ModifyDBInstanceInput, d *schema.
 	if d.HasChange("password") {
 		needsModify = true
 		// With ManageMasterUserPassword set to true, the password is no longer needed, so we omit it from the API call.
-		if v, ok := d.GetOk("password"); ok && len(v.([]interface{})) > 0 && v.([]interface{}) != nil {
+		if v, ok := d.GetOk("password"); ok {
 			input.MasterUserPassword = aws.String(v.(string))
 		}
 	}
diff --git a/internal/service/rds/instance_test.go b/internal/service/rds/instance_test.go
index bcf6240088ca..24d2bbb6f56f 100644
--- a/internal/service/rds/instance_test.go
+++ b/internal/service/rds/instance_test.go
@@ -971,10 +971,10 @@ func TestAccRDSInstance_password(t *testing.T) {
 				ExpectError: regexp.MustCompile(`MasterUserPassword is not a valid password because it is shorter than 8 characters`),
 			},
 			{
-				Config: testAccInstanceConfig_password(rName, "valid-password"),
+				Config: testAccInstanceConfig_password(rName, "valid-password-1"),
 				Check: resource.ComposeAggregateTestCheckFunc(
 					testAccCheckInstanceExists(ctx, resourceName, &v),
-					resource.TestCheckResourceAttr(resourceName, "password", "valid-password"),
+					resource.TestCheckResourceAttr(resourceName, "password", "valid-password-1"),
 				),
 			},
 			{
@@ -988,6 +988,13 @@ func TestAccRDSInstance_password(t *testing.T) {
 					"skip_final_snapshot",
 				},
 			},
+			{
+				Config: testAccInstanceConfig_password(rName, "valid-password-2"),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckInstanceExists(ctx, resourceName, &v),
+					resource.TestCheckResourceAttr(resourceName, "password", "valid-password-2"),
+				),
+			},
 		},
 	})
 }