The attack was reported at about 2:10 a.m. near Font Boulevard and Tapia Drive.
The 20-year-old victim was walking down the street when three suspects in a vehicle approached him and began calling out homophobic slurs, police spokesman Officer Albie Esparza said.
The suspects then exited the vehicle and began punching and kicking the victim while one reached into the victim's pocket and took his smartphone, Esparza said.
The suspects then fled and have not been found, he said.
The victim suffered minor injuries in the attack but did not require hospitalization, according to Esparza.
One of the suspects is described as a black man between 20 and 25 years old who is about 5 feet 9 inches tall and weighs roughly 140 pounds. He has a thin goatee and was wearing an olive-color, button-down long-sleeve shirt with a crew neck undershirt and a beige bandana, Esparza said.
The victim described the second suspect as a white man about 5 feet 10 inches tall and weighing about 150 pounds with a "high and tight" haircut, police said. He was wearing a gray pullover hooded sweatshirt with a baseball diamond on it and baggy blue jeans.
The third suspect is described as a Hispanic man about 5 feet 8 inches tall and 160 pounds, who was wearing a tan shirt and baggy pants.
Their car is described as a four-door, cream-colored Oldsmobile sedan, possibly a late 1970s model, Esparza said.
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.