Shocking footage uploaded to social media showed a man staggering towards the tram doors at Castle Square before attempting to push the button.
The man stumbles forward into the tram doors before it sets off, leaving him to lurch alongside the moving carriageway.
As the tram carries on the man then loses his footing and falls into the tram tracks and underneath the moving tram.
Sheffield Supertram said that the driver stopped the tram as soon as the man fell underneath and they have launched an investigation into the incident.
A spokesperson for Supertram said: "We were aware of this incident that occurred over the weekend. Safety is our absolute priority and we have already begun an investigation into the circumstances surrounding the incident.
“Although not shown in this footage, our own CCTV footage shows that the driver stopped the tram as soon as the person fell over - the man pictured was not injured and walked away from the stop.
"We'd like to take the opportunity to remind customers about the safe use of trams. Once the doors have closed and the tram is ready to depart, customers should not attempt to board.”
Trams were held between Castle Square and Cathedral during the incident with trams delayed for 15 minutes as a result.