The 1983–84 Long Island Blackbirds men's basketball team represented Long Island University during the 1983–84 NCAA Division I men's basketball season. The Blackbirds, led by head coach Paul Lizzo, played their home games at the Athletic, Recreation & Wellness Center and were members of the ECAC Metro Conference. They finished the season 20–11, 11–5 in ECAC-M play to capture the regular season championship. They also won the ECAC Metro tournament to earn an automatic bid in the 1984 NCAA tournament where they lost in the play-in round to Northeastern, 90–87.