The three were shot outside the Louis Armstrong Houses just after 4:30 a.m. Wednesday.
Police say the 15-year-old girl was shot in the torso and taken to Brookdale Hospital, where she was listed in serious but stable condition.
The two men, ages 21 and 17, were reportedly taken to Kings County Hospital with non-life threatening injuries.
The 21-year-old was shot in the buttocks and the 17-year-old in the elbow and left shoulder.
A fourth person, a 17-year-old girl, may have sustained a graze wound to the hand. She was taken to Woodhull Hospital to be checked out.
No arrests were immediately made.