The robbery was reported at about 10:50 a.m. in the 100 block of Sixth Street.
The suspect, described as a man around 40 years old, entered the business and ordered a cookie, then paid for it. But as the employee opened the cash register, the suspect leapt over the counter and grabbed money out of the register, according to police.
A struggle ensued between the employee and suspect, who was eventually able to flee with some cash and was last seen headed north on Sixth Street toward Mission Street, police said.
Anyone with information about the robbery is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.