The 17-year-old victim was walking in the 5800 block of Mission Street about 9:38 p.m. when a man began to follow him, police said.
The man then put a mask on and punched the boy in the head, police said, knocking him to the ground.
The victim wrestled with the suspect but the suspect was able to take the victim’s cellphone and flee the scene northbound on Mission Street, police said.
The victim sustained an injury to his head and some abrasions on his face, but the injuries were not life threatening.
No arrest has been made.