Iron Ore Company of Canada, which owns the train, identified him on Friday as Enrick Gagnon, 45. He had worked for the company since 1997.
Parts of the train carrying diesel fuel fell into the Moisie River on Thursday, leaving a silvery layer of oil floating on the water.
Divers were unable to get into the water on Friday because it was too dark after the land near the river had been declared safe.
The train was made up of three locomotives and 240 empty cars.
The lead locomotive had a capacity of 17,000 litres and ended up fully submerged in the river.
It was unclear how many litres it contained at the time of the accident near Sept-Iles, about 900 kilometres from Montreal.
The locomotive behind it, which also had a capacity of 17,000 litres, was partially submerged.
An IOC spokeswoman said initial information indicates a landslide caused the derailment in the largely inaccessible area.
A spokesman for the Quebec Environment Department did not know how much diesel was in the river, although he said oil extended for about 20 kilometres out from shore.