The 40-year-old Melton man was stabbed and died not far from Melton Station on Staughton Street in Melton South after 2.35am.
The Homicide Squad are investigating the incident and have cordoned off a platform at Melton Station along with the carpark.
They believe the man had an interaction with an unknown man while walking through the train station about 2.30am.
It is believed the unknown male approached the victim and stabbed him in the upper body.
Detectives are calling for witnesses following the incident.
They specifically want to speak with a group of four males, perceived to be of African appearance, who are believed to have been with the attacker at the southern end of the train station just prior to the incident.
Anyone who was in the area at the time, or has dash cam footage for information to call Crime Stoppers on 1800 333 000 or log onto www.crimestoppersvic.com.au