Investigators say the two met while walking near East 102nd Street and Avenue M in Canarsie on Friday, November 1, around 11:30 p.m.
The man walked the young teen to a friend's house, where he sexually assaulted her.
She was treated at the hospital.
The suspect is described as a black male in his early to mid 20s, approximately 5-foot-10 and 165 pounds with a thin build, long dreadlocks and a goatee.
He was last seen wearing a red bubble jacket, dark jeans and multi-colored sneakers.
Anyone with information about the identity of this man is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
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