A three-component Mannich-type reaction of aromatic aldehydes, aromatic amines, and ketones was catalyzed by a novel functionalized ionic liquid, 3-(N,N-dimethyldodecylammonium)propanesulfonic acid hydrogen sulfate ([DDPA][HSO4]) at room temperature to give various beta-amino carbonyl compounds in good yields. The catalyst could be reused at least six times without noticeably reducing catalytic activity.