diff --git a/aws/resource_aws_db_parameter_group_test.go b/aws/resource_aws_db_parameter_group_test.go
index 1d330bfc7cc..7348569d4ff 100644
--- a/aws/resource_aws_db_parameter_group_test.go
+++ b/aws/resource_aws_db_parameter_group_test.go
@@ -413,6 +413,10 @@ func TestResourceAWSDBParameterGroupName_validation(t *testing.T) {
 			Value:    "testing--123",
 			ErrCount: 1,
 		},
+		{
+			Value:    "testing__123",
+			ErrCount: 1,
+		},
 		{
 			Value:    "testing123-",
 			ErrCount: 1,
diff --git a/aws/validators.go b/aws/validators.go
index 7ea9873eedb..b832737036a 100644
--- a/aws/validators.go
+++ b/aws/validators.go
@@ -100,9 +100,9 @@ func validateTagFilters(v interface{}, k string) (ws []string, errors []error) {
 
 func validateDbParamGroupName(v interface{}, k string) (ws []string, errors []error) {
 	value := v.(string)
-	if !regexp.MustCompile(`^[0-9a-z-]+$`).MatchString(value) {
+	if !regexp.MustCompile(`^[0-9a-z-_]+$`).MatchString(value) {
 		errors = append(errors, fmt.Errorf(
-			"only lowercase alphanumeric characters and hyphens allowed in %q", k))
+			"only lowercase alphanumeric characters, underscores and hyphens allowed in %q", k))
 	}
 	if !regexp.MustCompile(`^[a-z]`).MatchString(value) {
 		errors = append(errors, fmt.Errorf(
@@ -112,6 +112,10 @@ func validateDbParamGroupName(v interface{}, k string) (ws []string, errors []er
 		errors = append(errors, fmt.Errorf(
 			"%q cannot contain two consecutive hyphens", k))
 	}
+	if regexp.MustCompile(`__`).MatchString(value) {
+		errors = append(errors, fmt.Errorf(
+			"%q cannot contain two consecutive underscores", k))
+	}
 	if regexp.MustCompile(`-$`).MatchString(value) {
 		errors = append(errors, fmt.Errorf(
 			"%q cannot end with a hyphen", k))