The robbery was reported at 12:33 p.m. Thursday in the 700 block of Jackson Street.
The 55-year-old victim was walking when a suspect approached from behind and grabbed her purse, according to police.
The suspect fled to a waiting vehicle driven by a second suspect, while a female suspect who served as a lookout also entered the vehicle after the purse snatcher, police said.
The suspects, two men and a woman in their 20s, fled in the car, a 1990s-model four-door sedan, and had not been found as of this morning, according to police.
The victim was not injured in the robbery.
Anyone with information about the case is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.