The robbery was reported at 3:53 p.m. near Leland Avenue and Peabody Street.
The boy was approached by another juvenile who pulled out a gun.
The boy tried to flee but was chased down by the armed suspect and three others, who took his skateboard and then ran away, according to police.
The victim was not injured, and the suspects had not been found as of this morning, police said.
Anyone with information about the case is asked to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.