The French scrum-half marked his first start following his summer move from Biarritz by scoring and converting the crucial try for victory at Sixways.
With just 12 minutes remaining Tigers were trailing 17-12 and were down to 14 men following a yellow card for fly-half Toby Flood.
But, after some sustained Tigers pressure near the Worcester line, Dupuy found a gap in the home sides defence to touch down before adding the conversion for what proved to be the winning points.
He said: The conversion was difficult because I was tired, very tired. I had a lot of cramp. It was good to score.
The try was not important for me, but for the team it was very important. We were down to 14 men with a yellow card so it was a good moment to score.
When I took the ball I watched the prop but the prop didnt watch me, so I dummied and got the ball down.
Dupuys score ensured a third successive win from the start of the Guinness Premiership season for Tigers.
That is just the kind of form head coach Heyneke Meyer would have wanted with two tough contests coming up at Welford Road against London Wasps and local rivals Northampton Saints in the space of five days.
Defending Guinness Premiership champions Wasps are first up at Welford Road on Friday (8.05pm kick-off) and Dupuy said: The game against Wasps is very important for the supporters of the team, and for me I will see my friend Serge Betsen.
To reserve your ticket for the games against London Wasps and Northampton Saints call the Tigers ticket office now on 08701 28 34 30, or email [email protected]