The sexual assault happened at 5:00 a.m. on Saturday in the vicinity of Gerard Avenue and E. 158 Street.
According to investigators, the suspect followed the 27-year-old victim into the lobby of the building, forced her into a stairwell, sexually assaulted her, and then fled on foot.
The suspect is described as a black man in his 30s, 180-210 lbs, 5'8"-5'10" and was wearing a dark-colored baseball cap with a white stripe, a black jacket, blue jeans, and tan construction boots.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477). You can also text tips to CRIMES (274637), then enter TIP577.