The victim, a 54-year-old Hercules woman, told police that her car had been parked overnight in the 1500 block of Chelsea.
When she returned to her car on Tuesday morning, she found the swastika, which appeared to have been scratched into the hood with a key, Abetkov said.
He estimated that the symbol was about 2 feet by 2 feet and covered most of the car's hood.
Abetkov said there was nothing on the vehicle that would identify the victim as Jewish, but based on her religious faith, police are investigating the incident as a hate crime.
Officers canvassed the neighborhood Wednesday morning and again that evening, but so far haven't found anybody who saw the crime occur, Abetkov said.
No other similar incidents have been reported recently in Hercules or any surrounding areas, Abetkov said.
Anyone with information about the case is asked to call Abetkov at (510) 799-8279.