Investigators have been told a man with a tyre iron entered the service station on Frankston Flinders Road just after 2am.
He approached the male attendant and demanded cash from the till before attempting to jump the counter.
The attendant pushed the man back before the offender tried to strike him with the tyre iron but missed.
The offender then ran out of the shop and into a waiting late model white Holden station wagon being driven by another person.
Detectives have released a CCTV image of a man they wish to speak to in relation to the incident.
Anyone with information about the incident is urged to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au