The incident happened just after 9pm on Thursday, November 6.
Officers would like to speak to the man pictured, as they believe he may have information that would help their investigation.
Anyone who recognises him is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 140 of 6 November.
A spokesperson for the British Transport Police said: “Detectives investigating the sexual assault of a man on a train to Euston have today released these images in connection.
“Just after 9pm on Thursday 6 November, a disabled man was sexually assaulted while on a train from Liverpool to Euston railway station.
“Officers would like to speak to the man pictured, as they believe he may have information that would help their investigation.
“Anyone who recognises him is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 140 of 6 November.
“You can also contact Crimestoppers anonymously on 0800 555 111.”
