Emergency services rushed to the railway station at around 8pm on Tuesday after two people jumped from a platform.
The casualties, who have not yet been named, were pronounced dead at the scene.
Early reports state that the two people were hugging as they jumped from the platform in front of the train.
Tributes for the pair flooded in on Facebook but one woman was left disappointed by a few 'ignorant' comments surrounding the incident.
Melissa Shaw criticised comments on social media questioning 'what goes through people's heads' before sharing a powerful message about mental health.
She commented: "What world do we live in with that ignorance? Mental illness is hard.
"People manage better then others. What people should be doing is supporting and telling people to speak out about it and seek help.
"No wonder people feel like there's no other option.
"Yes, I feel for people who have witnessed this, but also remember the people who were so down and didn't see a way out and would not have even realised the impact it would have on others."
A British Transport Police spokesman said: "Officers were called to Doncaster railway station to reports of two people being struck by a train.
"The call came in to police at 8.19pm and officers attended alongside paramedics.
"Sadly two people were pronounced dead at the scene.
"Officers will now work to establish their identities and inform their next of kin.
"The investigation into how they came to be on the track is underway and a file will be prepared for the coroner."
Samaritans (116 123) operates a 24-hour service available every day of the year.