The suspect has robbed or tried to rob five teens and a 12-year-old in the Carroll Gardens section.
All of the incidents happened this past Monday and Wednesday.
In three of the robberies, the suspect threatened the victims with a knife or a box cutter. Most of the incidents happened between 7 a.m. and 9 a.m., with one taking place in the afternoon.
No injuries have been reported.
The suspect is described as a black male between the ages of 18 and 23, approximately 5-foot-10 with a freckled face.
Anyone with information is asked to call Crime Stoppers at 1-800-577-TIPS (8477).