British Transport Police are hoping to speak to a man as they investigate an incident on a train between Whitby and Middlesbrough at around 10.30pm on Friday 11 July.
A man, who police say may have been under the influence of alcohol, verbally abused staff on the train and then slapped one of them.
The man continued to shout at the victim and slapped him again before other passengers intervened.
He got off the train at Middlesbrough with a woman.
Anyone who recognises the man in the CCTV image is asked to contact police.