The fatal incident occurred just south of the Wilmington station around 8:10 p.m.
The southbound Acela Express Train #2119 struck a male pedestrian described by Amtrak officials as a trespasser.
He was pronounced dead at the scene.
Rail traffic was halted in both directions.
Police and Amtrak officials are investigating.
The train originated in New York and was destined for Washington D.C.