But when Fabio Semenzato crossed with a minute remaining, and Kris Burton converted to give Treviso the lead, it looked as though the internationals' return would be in vain.
However with time virtually up Sexton kept his nerve and fired the ball through the uprights to give Leinster the points.
In the first half it was the home side who looked the more threatening and Treviso took a deserved 8-3 lead into the break.
Joe Schmidt clearly wanted a reaction from his team and got it almost immediately as O'Driscoll crossed after just four minutes of the second half, and from there last season's RaboDirect PRO12 runners-up showed all their experience to keep the Italians at bay.
Treviso, who had started the season with a home success over reigning champions the Ospreys before losing at Munster last time out, got off the mark through fly-half Alberto Di Bernardo after a quarter of an hour.
Kevin McLaughlin was another of Leinster's international contingent in the starting line-up but when he was sent to the sin bin, Treviso took full advantage.
Although Di Bernardo missed a shot at goal, Azzurri back row Robert Barbieri crashed over for the first try of the game to extend the lead to 8-0.
On the half hour Sexton finally got Leinster on the board with a penalty and that was how it stayed until the break.
It was in the second half that Leinster showed their experience, with Ireland skipper O'Driscoll producing a trademark break from midfield to cross under the posts for his first try of the season.
Sexton converted to give the visitors the lead, and then extended that advantage with a penalty just before the hour mark.
Leinster were then dealt a blow as hooker Richardt Strauss had to be stretchered off, to be replaced by Sean Cronin.
Italy international Kris Burton was on the pitch by now and he kept his nerve on 66 minutes to reduce the Leinster lead to just two points.
However with five minutes remaining Sexton was again on target with a penalty to stretch the lead back to five points.
Replacement Semenzato then pounced with what looked like the winning try, converted by Burton, only for Sexton to break Italian hearts at the death.
|Benetton Treviso Score Card|
|Alberto di Bernardo||1||3|
|Leinster Rugby Score Card|