Sussex Police said a Bognor Regis man, aged 33, was punched in the face twice by a 17-year-old boy following an argument about the suspect’s girlfriend.
The assault took place at 11.15am on Friday, April 29 on the number 53 bus while it was in a lay-by near the bus station in Southgate.
The boy, from East Wittering was arrested on suspicion of causing Actual Bodily Harm (ABH) and released on police until May 23 pending further enquiries.
PC Stephen McNally from Chichester Police said: “I am appealing to anyone who was on the bus and witnessed the assault to contact police immediately.”
Anyone who can help should contact Sussex Police on 0845 60 70 999 independent charity Crimestoppers on 0800 555 111.