The victim was travelling on a westbound Central line train between Shepherd’s Bush and Ealing Broadway on Saturday, September 18 when the assault happened.
At 7pm, three men boarded the train and one member of the group began racially abusing the passenger, officers said.
When he attempted to report the incident, the man assaulted him, hitting his phone against his head and repeatedly kicking and punching him to the floor.
The two other group members then got involved further attacking the victim, said British Transport Police officers.
The group left the train at Ealing Broadway afterwards.
Police released CCTV images on Tuesday of men they say may have information which could help their investigation.
Anyone who recognises them or has information is being asked to contact officers by texting 61016 or calling 0800 40 50 40, quoting reference 594 of 18/09/21. Alternatively, the Crimestoppers charity can be contacted anonymously on 0800 555 111.