Emergency services were called to Dore and Totley railway station shortly before 11am morning following reports of a man being struck by a train.
A spokesman for British Transport Police said: "The call came into police at 10.56am.
"Officers attended alongside paramedics but sadly a 28-year-old man was pronounced dead at the scene. His death is not being treated as suspicious.
"Officers are now working to formally identify the man and inform his next of kin. A file will be prepared for the coroner."
All lines between Sheffield and Manchester and Sheffield and Chesterfield were closed while emergency services dealt with the incident.
Affected services included East Midlands Trains between Norwich and Liverpool South Parkway, Northern services between Sheffield and Manchester Piccadilly and TransPennine Express trains between Cleethorpes and Manchester Airport.
All lines re-opened earlier this afternoon.