The assault happened in Burton Stone Lane, at about 10pm last night (Wednesday).
The 68-year-old man was sitting at a bus stop when the attack happened, a spokesman for North Yorkshire Police said.
Three youths attacked him, causing cuts to his head and face.
A pair of his glasses were also broken during the assault.
The spokesman said enquires are ongoing to trace the three youths involved.
But the force has appealed for information to help officers establish the full circumstances surrounding the offence.
They are searching for witnesses who saw three young men, aged between 14 to 18, dressed in mainly dark clothing last night.
Anyone with information is asked to contact North Yorkshire Police on 101, or Crimestoppers anonymously on 0800 555 111.