The alleged victim was sitting in his car at a shopping centre car park on the Nepean Highway in Cheltenham at 10pm yesterday, when a group of three teenagers approached him, police said.
He was allegedly threatened with a pair of pliers before he was pulled from his grey Mazda sedan.
The teenagers then allegedly fled the scene in his car, stopping to pick up two other teenagers on the way.
The car was later found abandoned at the intersection of Hammond Road and Cheltenham Road in Dandenong.
Two 14-year-old girls turned themselves into a Protective Services Officer at a nearby train station, where they were arrested.
Both of them were released with an official caution for theft of a motor vehicle.
A 14-year-old boy and a 16-year-old boy were arrested on Lonsdale Street in Dandenong at 3am that same night.
They are being interviewed by police, and are expected to be charged with aggravated carjacking and theft of a motor vehicle.
An application to remand the boys in custody will be made today.
Police are still searching for one teenager.