Police have been told the girl was waiting at a bus stop near Somerville train station about 4pm on Tuesday when a van pulled up alongside her.
A man in the van allegedly told the girl he was there as a bus service replacing the train.
The van allegedly had a Public Transport Victoria sticker on it.
The teenager refused to get in the van and the men drove away.
The actual train replacement bus arrived a short time later and the girl reported the incident to police.
Police are calling for anyone with CCTV, dashcam footage or any other information to come forward.
One of the men was described as Caucasian in appearance, balding with a heavy build and wearing a blue jacket and orange tabard.
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The second was perceived to be Caucasian and had brown hair.
The girl’s school warned parents about the incident yesterday.
Victoria Police Senior Constable Scott Walters told 3AW the incident “is alarming”.
“We are looking into it and we are treating it very seriously,” he said.
“We’ve had the replacement buses running down here for some time.
“To think someone is maybe taking advantage of that is quite concerning.”