Tuilagi played a key role in the Tigers' domestic success last term
A late Alesana Tuilagi try saved Leicester as they narrowly avoided a Heineken Cup upset at Treviso.
Matt Smith and Craig Newby touched down early on for the Tigers but a Tomasso Benvenuti try and Chris Burton's boot had Treviso level 13-13 at the break.
Martin Castrogiovanni and Ben Youngs went over for the English champions but Benvenuti crossed again for the hosts.
A Benvenuti drop-goal looked like being decisive but Tuilagi's heroics stole a bonus-point win with two minutes left.
Billy Twelvetrees was a late replacement for Toby Flood at outside-half for Leicester, while Horacio Agulla was promoted from the bench to deputise at centre for Dan Hipkiss, who was ruled out in the warm-up.
The visitors did not appear to be affected by those late changes, though, as they took a second-minute lead - centre Smith exploiting a gap in the Treviso midfield to run in from 40 metres out.
Twelvetrees could not add the extras and the home side edged ahead when an Alberto Sgarbi burst was finished off by young centre Benvenuti before Burton converted.
The 21-year-old Twelvetrees got off the mark with a 14th-minute penalty before Burton saw a three-point attempt hit the post.
Leicester extended their lead to six points when back rower Newby picked up from a ruck to force his way over.
Twelvetress was wide with the kick, and he and Burton exchanged misses off the tee before the latter drew the sides level with a fine drop.
Treviso ended the half without Robert Barbieri after the flanker was sin-binned for a ruck infringement, and although Burton kicked another drop straight after the restart, Tigers took advantage of the extra man when Italy international Castrogiovanni crashed over.
Twelvetrees converted to make it 20-16 but when Barbieri returned the impressive Benvenuti weaved through the Tigers' defence to run in under the posts and Burton made no mistake with the kick.
There was no let-up in this pulsating encounter, however, as Leicester again put the phases together and were quickly rewarded with a bonus-point try.
Thomas Waldrom picked up at the base of a scrum to feed Youngs who sped in from 18m out - Twelvetrees obliging with two more points.
Burton took his tally to 16 from a penalty and a Benvenuti drop put Treviso in front by a point with 13 minutes remaining.
But Tom Croft initiated a counter-attack on the left which eventually found Tuilagi on the overlap before the giant Samoan winger stormed over from 30m out.
Twelvetrees landed his third conversion of the match and the Italians could not muster any more late drama and had to settle for a point.
Leicester director of rugby Richard Cockerill: "If anyone was under any illusions about Treviso, they won't be now. We didn't take them lightly at all - they have a game plan and they play it well. Their league form is no fluke.
"We needed to score in the last couple of minutes to win the game and we ran out from under our own posts, held on to it and finished it well. We must have gone through a dozen phases to score. That says a lot for the guys.
"Many other sides might have given up in that situation, but we kept going, we ept our discipline and got the result.
"We should have been better defensively and we have to control our possession etter. But the win makes sure we are upbeat going into next week's game at home tothe Scarlets."
Benetton Treviso: McLean, Nitoglia, Benvenuti, Sgarbi, Vilk, Burton, Semenzato, Rouyet, Ghiraldini, Cittadini, A. Pavanello, van Zyl, Barbieri, Zanni, Derbyshire.
Replacements: Maddock for McLean (48), Picone for Nitoglia (78), Botes for Semenzato (48), Sbaraglini for Rouyet (35), Vidal for Ghiraldini (48), Di Santo for Cittadini (48), E. Pavanello for A. Pavanello (61). Not Used: Filippucci.
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