diff --git a/fuzz/fuzz_seeds/postgres_alter_extension.sql b/fuzz/fuzz_seeds/postgres_alter_extension.sql
index 94794655bc..4fc0e0d314 100644
--- a/fuzz/fuzz_seeds/postgres_alter_extension.sql
+++ b/fuzz/fuzz_seeds/postgres_alter_extension.sql
@@ -37,3 +37,4 @@ ALTER EXTENSION citext DROP OPERATOR FAMILY of USING btree;
 ALTER EXTENSION citext ADD CAST (int AS text);
 ALTER EXTENSION citext ADD TRANSFORM FOR int LANGUAGE plpgsql;
 ALTER EXTENSION citext DROP TYPE public.ty;
+ALTER EXTENSION citext ADD DOMAIN public.dom;
diff --git a/src/ast/ddl.rs b/src/ast/ddl.rs
index 75ce3c306d..d6394da162 100644
--- a/src/ast/ddl.rs
+++ b/src/ast/ddl.rs
@@ -4947,6 +4947,8 @@ pub enum AlterExtensionMember {
     Conversion(ObjectName),
     /// `DATABASE object_name`
     Database(Ident),
+    /// `DOMAIN object_name`
+    Domain(DataType),
     /// `EVENT TRIGGER object_name`
     EventTrigger(Ident),
     /// `EXTENSION object_name`
@@ -5058,6 +5060,7 @@ impl fmt::Display for AlterExtensionMember {
             AlterExtensionMember::Collation(name) => write!(f, "COLLATION {name}"),
             AlterExtensionMember::Conversion(name) => write!(f, "CONVERSION {name}"),
             AlterExtensionMember::Database(name) => write!(f, "DATABASE {name}"),
+            AlterExtensionMember::Domain(data_type) => write!(f, "DOMAIN {data_type}"),
             AlterExtensionMember::EventTrigger(name) => write!(f, "EVENT TRIGGER {name}"),
             AlterExtensionMember::Extension(name) => write!(f, "EXTENSION {name}"),
             AlterExtensionMember::ForeignDataWrapper(name) => {
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index 78a5e5815d..04b5c89e48 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -12556,6 +12556,8 @@ impl<'a> Parser<'a> {
             ))
         } else if self.parse_keyword(Keyword::DATABASE) {
             Ok(AlterExtensionMember::Database(self.parse_identifier()?))
+        } else if self.parse_keyword(Keyword::DOMAIN) {
+            Ok(AlterExtensionMember::Domain(self.parse_data_type()?))
         } else if self.parse_keywords(&[Keyword::EVENT, Keyword::TRIGGER]) {
             Ok(AlterExtensionMember::EventTrigger(self.parse_identifier()?))
         } else if self.parse_keyword(Keyword::EXTENSION) {
diff --git a/tests/sqlparser_postgres.rs b/tests/sqlparser_postgres.rs
index b813de3ccf..ebeb6dab49 100644
--- a/tests/sqlparser_postgres.rs
+++ b/tests/sqlparser_postgres.rs
@@ -13547,6 +13547,7 @@ fn alter_extension_member_round_trip_forms(action: &str) {
         format!("ALTER EXTENSION ext_name {action} COLLATION schema.en_US"),
         format!("ALTER EXTENSION ext_name {action} CONVERSION conv"),
         format!("ALTER EXTENSION ext_name {action} DATABASE db_name"),
+        format!("ALTER EXTENSION ext_name {action} DOMAIN my_domain"),
         format!("ALTER EXTENSION ext_name {action} EVENT TRIGGER trg"),
         format!("ALTER EXTENSION ext_name {action} EXTENSION other_ext"),
         format!("ALTER EXTENSION ext_name {action} FOREIGN DATA WRAPPER fdw"),
@@ -13888,6 +13889,10 @@ fn parse_alter_extension_add_member() {
             "ALTER EXTENSION ext_name ADD CAST (INT AS INT",
             "Expected: ), found: EOF",
         ),
+        (
+            "ALTER EXTENSION ext_name ADD DOMAIN",
+            "Expected: a data type name, found: EOF",
+        ),
         (
             "ALTER EXTENSION ext_name ADD OPERATOR CLASS",
             "Expected: identifier, found: EOF",