The robbery was reported at about 8:50 p.m. at a business in the 3300 block of Fillmore Street between Lombard and Chestnut streets.
A suspect entered the store, took out a handgun and ordered two employees, a 21-year-old woman and 24-year-old man, to the rear of the business, according to police.
He ordered the male employee to open the company's safe and the victim complied, handing over cash, police said.
The suspect, described as a man in his early 30s, fled and had not been found as of this morning.
Neither employee was injured in the robbery, according to police.
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.