They think a person placed the faux-bomb at the door before ringing the bell and fleeing.
The firefighter's family and neighbors were evacuated from the area while the bomb squad investigated the device for about two hours early Wednesday morning, according the Daily News.
It was not immediately clear why the firefighter's home was targeted. The man and his family did not appear to have any apparent combative disputes with anyone, a police spokesman said.
The Bay Ridge bomb scare comes in the wake of Monday's twin bombings at the Boston marathon that killed three and injured over 170 others. New York, along with many other cities, was put on high alert afterward.
New York Police Commissioner Ray Kelly said Tuesday that since the Boston bombings the NYPD received 77 reports of suspicious packages around the city. During the same period last year, cops received only 21.
Cops described a person of interest in the Bay Ridge bomb hoax as an adult man with short cropped hair last seen wearing dark clothing.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).