Mandurah Police have called on the public to help their investigation into an incident between a taxi driver and his passenger near Monkey Bar on July 28.
About 2.15am, an incident occurred between the duo adjacent to the Pinjarra Road pub.
Police will allege a man, in his 40s, punched the driver several times.
A number of people were in the area at the time and assisted the taxi driver following the incident.
The offender has been described as a bald man, about 170 centimetres in height, of solid build and clean shaven.
The man was wearing a brown jacket and jeans at the time of the incident.
Police have urged anyone with information, that could assist the investigation, to call the local station on 9581 0222 or Crime Stoppers on 1800 333 000.
Alternatively, people can make anonymous reports by visiting the website at www.crimestopperswa.com.au.