The attack was reported at about 12:50 a.m. in the 1200 block of Market Street, between Eighth and Ninth streets.
The 31-year-old victim got into an argument with two other men, then attempted to flee, according to police.
The suspects gave chase and after one of them hit the victim with the skateboard, knocking him to the ground, the other suspect stabbed the victim in the back, police said.
The victim was taken to San Francisco General Hospital to be treated for his injuries, which are not considered life-threatening.
The suspects fled and had not been found as of this morning, police said.
Anyone with information about the attack is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.