The crash occurred shortly before 8 p.m. Wednesday at Sunset Boulevard and Sunset Plaza Drive, Los Angeles County Sheriff's spokesman Sgt. Joseph Morien told The Associated Press.
The pitcher was taken to Cedars-Sinai Medical Center, where he was examined and released, Deputy Mark Pope said Thursday.
Morien said he was taken to the hospital "just to be checked out if he had injuries or not."
Giants manager Bruce Bochy said Zito came to the ballpark before Thursday's season opener against the Dodgers.
"He felt pretty good. He had some soreness," Bochy said. "It's two to three days before you know the extent of these accidents."
Bochy said Zito left the ballpark and was scheduled to have an MRI exam later.
Cedars-Sinai declined to say if Zito was treated there. City News Service said the other driver wasn't hurt.
Morien said Zito was not at fault, but the officer did not provide other details of the crash. He said Zito's car had major damage.
"He was really upset. It happened so fast," said Bochy, who spoke to Zito after the accident. "Somebody ran a red light. He was taking a left turn."
The crash is still being investigated, and Morien said he didn't know if the other driver would be cited.
Zito, a former AL Cy Young winner and the team's No. 4 starter, is scheduled to start Sunday's series finale. Bochy said he was optimistic Zito would be able to pitch.