The shooting happened around 10 p.m. Sunday in the parking lot of Mariscos La Ola on the 1700 block of McFadden Avenue at Lyon Street.
Officials said an argument inside the restaurant led to the shooting.
The victim, Esteban Navarrete, 35, was having dinner with friends when there was a confrontation. Navarrete's brother said there was a verbal fight inside the restaurant about which state in Mexico was better.
The fight became physical in the parking lot. Navarrete and his wife tried to leave to avoid the fight. As they got into their car, two suspects approached them and fired several shots, hitting Navarrete in the head.
The victim was transported to Western Medical Center in Santa Ana, where he remained in critical condition.
Investigators gathered evidence from inside a restaurant nearby where a bullet went through a window.
Anyone with information was urged to call Santa Ana police at (714) 245-8390. Callers can remain anonymous.