Benetton Treviso (12) 29
Tries: McLean, Williams Con: Botes 2 Pens: Botes 3
Drops: Burton 2
Leinster (10) 13
Try: Nacewa Con: Nacewa Pens: Nacewa 2
Sean O'Brien is tackled by Manoa Vosawai in Saturday's game in Italy
Leinster's poor start to the Magners League season continued as they were outgunned by new boys Treviso.
Isa Nacewa notched an early Leinster try but two Tobie Botes penalties and a brace of Chris Burton drop goals helped Treviso lead 12-10 at half-time.
Nacewa briefly restored Leinster's lead but another Botes penalty and a Luke McLean try put Treviso 22-13 ahead.
Leinster produced late pressure but Brendan Williams notched a breakaway try for Treviso at the death.
The defeat was Leinster's second in their opening three games and it's been a disappointing start for new coach Joe Schmidt who took over from Michael Cheika in the summer.
Leinster, with Gordon D'Arcy, Rob Kearney and Eoin Reddan making their first starts of the season, got off to the perfect start as Nacewa notched a second-minute try which he himself converted.
However, Treviso regrouped to take the lead by the 17th minute as two Botes penalties were split by Burton's drop goal.
Burton then slotted another drop goal in the 37th minute to extend Treviso's lead to 12-7 before Nacewa got Leinster scoring again in first-half injury-time.
Nacewa nudged Leinster ahead two minutes after the break with another successful penalty before the game started to open up.
Firstly, Treviso debutant Joe Maddock's jinking run into the Leinster 22 put the visitors under severe pressure but desperate defence kept the home side at bay.
Leinster immediately counter-attacked and Eoin Reddan only had to find Rob Kearney to ensure a certain try but the attempted reverse pass went to ground.
By the 50th minute, Treviso were ahead again as pressure yielded another penalty for Botes.
And Leinster were in real trouble four minutes later when McLean barged his way through some weak tackling to score a Treviso try.
For good measure, Botes added the difficult conversion to increase Treviso's lead to 22-13.
The 73rd-minute sin-binning of hooker Leonardo Ghiraldini gave Leinster a glimmer of hope of producing a late comeback.
However, Nacewa and Fergus McFadden both missed penalties and the Irish side failed to even earn the small consolation of a bonus point despite threatening the Treviso line in the closing seconds.
Indeed, Treviso had the final scoring say as Williams ran the full length of the field to score a breakaway try after more sloppy Leinster handling.
Granted Leinster were without several of their Ireland stars, including Brian O'Driscoll, but this was another concerning night for new coach Schmidt.
Benetton Treviso: Brendan Williams; Joseph Maddock, Tommaso Benvenuti, Alberto Sgarbi, Luke McLean; Kristopher Burton, Tobias Botes; Ignacio Fernandez Rouyet, Leonardo Ghiraldini (capt), Lorenzo Cittadini, Valerio Bernabo, Corniel Van Zyl, Robert Barbieri, Alessandro Zanni, Manoa Vosawai.
Replacements: Franco Sbaraglini for Rouyet (50), Enrico Pavanello for Berbano (50), Paul Derbyshire for Vosawai (70), Ezio Galon for Maddock (63).
Not used: Vidal, Di Santo, Semenzato, Picone.
Leinster: Rob Kearney; Isa Nacewa, Eoin O'Malley, Gordon D'Arcy, Luke Fitzgerald; Ian Madigan, Eoin Reddan; Cian Healy, John Fogarty, Mike Ross; Nathan Hines, Ed O'Donoghue; Rhys Ruddock, Shane Jennings (captain), Sean O'Brien.
Replacements: Richardt Strauss for Fogarty (47), Heinke van der Merwe for Healy (56), Simon Shawe for Ross (63), Mariano Galarza for Hines (73), Fergus McFadden for D'Arcy (56).
Not used: Keogh, Boss, D Kearney.
Referee: Peter Allan (SRU)