The man was spotted in surveillance photos.
Police say he has targeted two drug stores near each other in Marine Park.
About every two weeks, police say he enters a store, shows off a gun and demands pain medication.
He has been to each location twice.
The suspect is described as a white male, about 6-foot-1 and weighing 220 pounds. He has been seen wearing a black Northface jacket.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477). The public can also submit their tips by logging onto Crimestoppers website and at NYPDCrimeStoppers.com or by texting their tips to CRIMES (274637), then enter TIP577.