A sweet 16 party at a Harlem community center turned ugly early yesterday when a gunman shot three revelers, police said.

The suspect opened fire after a dispute erupted in the party room, which was bedecked with yellow and purple balloons and streamers,at 198 E. 121st St., at 2:30 a.m.

He shot a 21-year-old man in the head, and a 21-year-old woman and 16-year-old boy, each in the leg, before fleeing.

The first victim was in critical condition at St. Luke’s Hospital. The others are recovering at Harlem Hospital.