South Yorkshire Police has today released details of the incident, which occurred on Tuesday, May 24, in a bid to identify the attacker.
The 33-year-old victim boarded the Number 2 double decker bus from Maltby to Rotherham at 3.40pm at the Wickersley Road stop, heading towards Rotherham.
It is alleged that an unknown man then assaulted him while he was at the rear of the bus’s top deck.
And the violence continued when the victim got off the bus in Wellgate, where police said he is believed to have been subjected to a further assault by the same man.
The victim suffered bruising and swelling to his head, causing him to briefly lose consciousness.
The suspect was reported to have been wearing a red top.
Anyone who witnesses the incident is asked to contact South Yorkshire Police via 101 quoting incident number 709 of May 24, 2016.