The 33-year-old man from Barnsley was arrested on Saturday on suspicion of attempted rape before being bailed until January 20 as police enquiries continue.
British Transport Police said the ongoing investigation relates to an incident on Saturday November 19 and officers are continuing to appeal for information.
A 27-year-old woman and her partner were travelling on the delayed 10.24pm train from Sheffield to Leeds, which left Sheffield at 10.40pm from platform 1B.
Before the train left Sheffield, the victim’s partner went to the toilet and left her sitting by the window.
While he was away, another man sat down next to the victim. The man allegedly attempted to rape the woman .
The woman's partner returned from the toilet unaware of what had taken place and physically moved the man from his seat.
The woman and her partner got off the train at Swinton railway station but it is not known where the man got off the train.
He is believed to have been travelling with another man.
Police said the suspect is described as white, aged in his late twenties to early thirties, with brown hair and was wearing a blue Puffer jacket.
He was with another man, also white, aged in his late twenties to early thirties and wearing a black Puffer jacket.
Det Insp Mick Jackson of British Transport Police, said: “We have spoken to a number of witnesses already, but I believe there are still people who were on the train or perhaps on the platform who may have seen what took place, or have information about what happened prior to or after the incident which could help us to piece together what happened.
“Incidents of this nature on the railway network are rare, and it is vital that we establish the exact circumstances of what happened. The victim continues to be supported by specially trained officers as the investigation continues.
“I would like to hear from anyone who was on the train who has not yet spoken to police, who may have seen or heard anything that could help with our investigation. If you recognise the description of the offenders or have any information, no matter how insignificant it may seem to you, please contact me either by calling 0800 40 50 40 or by texting 61016 quoting reference 147 24/11/16.”