Police said the victim was inside his unit in a building near West 145th Street and Edgecombe Avenue in Upper Manhattan just after 8 a.m. when he heard a knock at the door.
When he opened the door, one of the suspects pulled out a gun and demanded money and the victim's cellphone while the other suspect stayed at the front of the apartment and acted as a lookout.
The victim handed the phone and $270 in cash over before they left.
The 90-year-old man was not hurt.
Police said he had just moved into the apartment eight days ago and is a veteran of the Korean War.
Police are asking anyone with information to call Crime Stoppers at 1-800-577-TIPS (8477).
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