Police said the victim, Juan Galdos of Rockville Centre, was pronounced dead at the scene.
Detectives said the victim was crossing Merrick Road from north to south in a marked crosswalk at Oceanside Road when he was hit by a 2003 Peterbilt tractor trailer driven by a 59-year-old man.
The tractor trailer was eastbound in the right lane of Merrick Road at Oceanside Road when it struck Galdos, police said.
Safety checks were performed on the tractor trailer at the scene, police said, and the investigation is ongoing.
Detectives said there appears to be no criminality.