The robberies happened just minutes apart between 3 and 3:30 p.m. at 525 East 14th Street and 17 Stuyvesant Oval.
The victims say they were threatened with a weapon that looked like an ice pick.
The suspect waited outside the buildings for his victims and pretended to be on his cell phone before he followed them inside.
The suspect previously mugged four women in Co-op City and Peter Cooper Village.
Police have posted wanted signs throughout Co-Op City, hoping someone will take a second glance, recognize the thief and turn him in.
He is described as being in his 40s, about 6-foot tall and 250 pounds, with a close-cut beard and a green jacket.
Police ask anyone with information about the suspect to call Crime Stoppers at 800-577-TIPS.
You can also submit your tips by logging onto Crime Stoppers website at NYPDCrimeStoppers.com or by texting your tips to CRIMES (274637), and then entering TIP577.
All calls are strictly confidential.