A 22-year-old man was left needing hospital treatment after he was assaulted by three men wearing bandanas over their faces at Bookham station.
British Transport Police are appealing for information after the attack in the station car park at 11pm on Saturday April 13.
The victim's wallet was also stolen in the incident.
Detective Constable Rachel Smith, leading the investigation, said: "The victim was standing by his vehicle in the car park with some friends when he was approached by three men wearing bandanas covering their face.
"After confirming the victim's name, one of the men punched him before the other two men joined in. The victim then fell to the ground as the men continued their attack.
"One of the victim's friends stepped in to help, but was pushed back onto the car where she banged her head and received a torrent of abuse from the three men.
"During the incident, one of the men took the car keys from the ignition which they threw into a nearby garden. The victim's wallet was also stolen."
Officers are currently following a number of avenues of enquiry, including viewing CCTV footage from the train station and speaking with witnesses.
The three men are described as white, wearing dark clothing and were all thin in build and all about the same height. One of the men was wearing a black and white patterned bandana around his face. The other two men were also wearing face coverings. They were seen to enter and leave the scene on foot.
DC Smith is appealing for anyone with information to come forward.
"This was a nasty attack that left the victim with a broken nose and numerous cuts and bruises; he required hospital treatment for his injuries," she said.
"If you know something, or if you were in the area at the time, we would like to speak to you."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40 quoting 768 of 14/4/2013.
Alternatively they can contact the independent charity Crimestoppers anonymously on 0800 555 111.
