British Transport Police (BTP) are investigating reports that a passenger was headbutted at Accrington railway station.
Officers have released CCTV images of a man they want to speak about the incident which happened between 7pm and 7.10pm on August 23.
The assault left the victim with two black eyes, bruising and swelling around his face.
BTP said a train arrived at platform one and the victim walked to cross over the overbridge.
A spokesperson said: “While on the overbridge, the victim is approached by a man who headbutts him and punches him to the head a number of times.
“Officers believe the man shown in this CCTV image may have information which could help them investigate.”
Anyone who recognises the man should contact BTP by sending a text to 61016 or call 0800 40 50 40 quoting reference 701 of August 23.