Officers responded to a report of shots fired in the 33600 block of Eighth Street at about 11 p.m., according to the Union City Police Department.
Arriving officers found a 34-year-old man on the street who had been shot numerous times.
A medical unit from the Alameda County Fire Department administered first aid but the victim died at the scene, police said.
No one has been arrested in connection with the crime.
Anyone with information is urged to contact Union City police Detective Roberta Paul at (510) 675-5207.