A 19-year-old was electrocuted while travelling on the roof a local train between Tilak Nagar and Chembur railway stations on Sunday.
Shamsher Allam Abdul Shaikh, a resident of Govandi, died after coming in contact with high-tension wires.
Passengers said they saw Shaikh lying motionless, with smoke coming out of his body when the train pulled into Tilak Nagar station around 2.54pm.
Government Railway Police (GRP) personnel took him to Sion hospital, where doctors declared him dead.
Travelling on train rooftops in Mumbai is illegal and can attract a fine of between Rs200 and Rs500, or a jail term of three months, although no one has been imprisoned for the offence yet.