It happened at about 12:42 a.m. Monday on the New England Thruway in Mamaroneck.
Police say the man, identified as 20-year-old Maicol Encarnacion Garcia, of Richmond Hill, had stopped to change the tire when he was hit by the passing truck that kept going.
The southbound right lane of the Thruway was closed for the investigation, but it was later reopened.
Troopers are searching for the truck and the driver. It is unclear of the driver knew someone was struck.
Anyone who witnessed the collision is asked to call the Bureau of Criminal Investigation in Hawthorne at (914) 769-2600.
(The Associated Press contributed to this report.)