The incident happened around 2:30 p.m. Monday on Fulton Street in Bedford-Stuyvesant.
Authorities say the suspect was holding what could be a gun in his right hand as he cornered the 39-year-old victim, who had eight children with her at the time, inside the elevator.
The suspect removed the woman's jewelry and fled on a bicycle.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).
