The teenager was sitting in Marina Park in St Crispin's with a friend when a group of boys approached them.
One of the group shouted at the boy while another punched him in the back of the head. They carried out further assaults before the boy escaped.
As a result of the attack the boy sustained a broken nose and swollen lip.
Northamptonshire Police issued descriptions of two attackers and are appealing for witnesses to the incident which happened between 4.15pm and 5.45pm on January 11.
A police spokesman said: "One of the offenders was white, 6ft 2in, of a stocky build, with short blond/brown hair. He had a deep voice and a scar on his face. He was wearing a black tracksuit and white shoes, which had black on them.
"A second offender was black, 5ft 7in, of a medium build, with long hair which was spiked up. He was wearing a blue Puma tracksuit."
Anyone with information or who may have seen the incident can call Northamptonshire Police on 101 quoting reference number 20000020404.