The robbery was reported at about 9:10 a.m. in the first block of Western Shore Lane, a small street located near the intersection of Laguna Street and Geary Boulevard.
When the 49-year-old victim answered a knock at her front door, three suspects stormed in, according to police.
One had a gun and ordered the woman to lie on the floor. The other two suspects then went through her bedrooms and stole the woman's cellphone before the trio fled, police said.
The victim was not injured during 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.