The teenager was walking home along Rushams Road, Horsham, at about 1am this morning (Sunday, February 18), police said.
At the junction with Victory Road he was approached by a white male wearing a dark, possibly green, tracksuit and a dark sleeveless puffa jacket with hood up, according to police.
The suspect demanded money which the victim did not have, then demanded the boy’s phone, which he handed over, police confirmed.
The victim also sustained two stab wounds one to the back and one to his arm, according to police.
The suspect then made off up Victory Road.
The boy was treated for his wounds at the Royal Sussex County Hospital in Brighton and was discharged later that morning, police confirmed.
Detective Constable Mike Wyborn said: “This was frightening experience for the young boy although thankfully his injuries are not serious.
“If you were in the Rushams Road area around that time and saw anything, or if you have any other information, please contact us online or call 101, quoting serial 99 of 18/02.
“You can also contact the independent charity Crimestoppers anonymously on 0800 555 111.”
There is not currently believed to be any connection between this incident and another at around the same time in East Street, in Horsham town centre.