They incidents happened between November 24 and December 8 on Webster Avenue in the Claremont section.
The stores are just down the block from each other.
Police say after threatening workers with a gun, the suspect made off with about $6,500.
The targeted stores were a MA Webster Inc., which is a Boost Mobile store, and the Simple Mobile store. In one of the robberies, the suspect punched the store clerk in the face, giving the victim a swollen lip.
The suspect is described as a 25-year-old black male who is approximately 5-foot-10 to 6-feet tall and weighs about 185 pounds.
Anyone with information in regards to these incidents is asked to call the NYPD's Crime Stoppers Hotline at 800-577-TIPS.