A 53-year-old man from Wokingham has been arrested on suspicion of assault with following an incident outside Reading Railway Station late last month.
Thames Valley Police said that they are now appealing for witnesses to come forward.
The incident happened shortly after 11pm on Saturday, April 27.
Police said that there was a fight between two men took place on the pedestrian area between the station and Blagrave Street.
A man in his 50s was punched and sustained head injuries. He was taken to hospital, where he remains in a serious but stable condition.
The second man was arrested and has since been released under investigation.
Investigating officer Detective Constable Natalie Powell said: “This was a serious assault which has left a man in a serious condition in hospital, and we’d like to hear from anyone who saw the altercation.
“We know there were a number of people in the area at the time, and I would urge anyone with information to get in touch as they may have vital information to help our enquiries.”
Anyone with any information is asked to call 101 or report it online, quoting 43190126771.
Alternatively, call independent charity Crimestoppers on 0800 555 111 in confidence.