Police said the boy was cycling to school on a cycle path on Hob Moor near Hob Stone Court when a male cyclist clipped his back tyre.
Police said the man became verbally abusive before he stopped the boy and punched him in the jaw.
The incident happened just before 8.30am on Tuesday November 13, but police only released details yesterday (Nov 22)
A North Yorkshire Police spokeswoman, said: "We are requesting the public’s assistance to help establish the full circumstances surrounding the incident and are appealing for information which would assist officers to identify the man who assaulted the teenage boy."
The man is described as a thin white man, aged between 30 to 35, with ginger hair.
He was wearing blue cycle shorts and blue jumper.
He was riding a black coloured road bike which had panniers on the back of the bike.
Anyone with information that could assist the investigation should contact North Yorkshire Police on 101, select option 2, and ask for Amanda Popely.
Quote North Yorkshire Police reference number 12180212175.