The victim and a 15-year-old boy were transported to NorthBay Medical Center, located at 1200 B Gale Wilson Blvd., around 10:40 p.m.
Both were suffering from gunshot wounds, police said.
The man succumbed to his injuries, while the teen was treated for a gunshot wound to his shoulder and released, according to police.
An investigation at an undisclosed location in Fairfield where the shooting is believed to have occurred is ongoing, police said.
Anyone with information about the shooting is asked to call Fairfield police at (707) 428-7600 or the 24-hour tip line at (707) 428-7345.