The group of five or six boarded the 6.15pm service from Edinburgh Waverley to Glasgow Queen Street at Linlithgow station on Saturday, travelling to Falkirk High.
While on board the train they sang sectarian songs and acted in a threatening and abusive manner, British Transport Police (BTP) said.
The only description of the men BTP have is that they were all under the age of 40. Officers are reviewing CCTV from the train and the stations to try and identify those involved.
Constable Christopher Sutherland said: "There is no excuse for this sort of behaviour on public transport. This was a busy service and I am appealing for anyone who was on the train or at either station and witnessed this unwelcome behaviour to come forward."
Anyone with information can contact BTP on 0800 40 50 40 or anonymously via Crimestoppers on 0800 555 111.