It happened at 2:30 a.m. in Lake Ronkonkoma.
Police say Thomas Vaughan of Lake Grove was driving a 2007 Chevrolet Trailblazer westbound on Express Drive North, near Carroll Avenue, when his vehicle struck a male pedestrian who was in the lane of traffic.
The pedestrian was pronounced dead at the scene.
The identity of the victim is being withheld pending notification of next of kin.
The 59-year old Vaughan is charged with Driving While Intoxicated and will be arraigned at First District Court in Central Islip.