Saracens became the only English side to qualify for the quarter-finals of the Heineken Cup with a win in Treviso.
Sarries trailed by four points at half-time, Robert Barbieri and Tommaso Iannone touching down for the hosts and Mouritz Botha for the visitors.
David Strettle scored after the restart but Treviso rallied, Tobias Botes having a try disallowed.
However, the English champions managed to hold on to top Pool Five and secure a home clash in the last eight.
Fellow Premiership sides Harlequins and Northampton were eliminated on the final weekend of qualifying.
Owen Farrell opened the scoring with a penalty before Treviso number eight Barbieri scored the first try of the match, picking up from the base of the scrum and breaking through the tackle of Alex Goode.
Sarries went over for their first try after 16 minutes, Peter Stringer putting in Botha to touch down under the posts, before Farrell kicked the extras.
However, Treviso came storming back, Iannone going over in the corner after quick hands down the line.
Kris Burton kicked the conversion and when the Treviso fly-half added three more points with a long-range drop-goal it became clear the English champions were in for a testing afternoon.
Farrell popped over a penalty shortly before half-time, Treviso's scrum having disintegrated on the retreat, meaning the visitors trailed 17-13 with 40 minutes remaining.
Wing Strettle gave Saracens the perfect start after the break, zig-zagging over for a try after scrum-half Botes had a kick charged down. Farrell made the conversion.
Burton levelled the scores with a penalty after Saracens' scrum came under pressure, before Farrell reinstated his side's three-point lead with a penalty of his own.
Saracens' set-piece came under increasing pressure as the second half wore on and after another scrum demolition by the hosts, Antonio Pavanello would have been over for a try were it not for a heroic tackle by Stringer.
Two minutes later, Botes looked to have wriggled over only for it to be disallowed for obstruction and Farrell made the most of the let-off with a simple penalty at the other end.
Treviso continued to press for the win until the final whistle.
Saracens director of rugby Mark McCall: "I thought we were miles off where we normally are, and especially in the first half.
"The intensity wasn't there, and neither were the standards we normally expect.
"I was pretty disappointed at half-time. But then in the second half we dug in, and I have nothing but admiration for the way we got the job done."
Benetton Treviso: Nitoglia, Iannone, Benvenuti, Sgarbi, Williams, Burton, Botes, Rizzo, Ghiraldini, Cittadini, A. Pavanello, van Zyl, Vermaak, Zanni, Barbieri.
Replacements: Di Bernardo for Iannone (75), Semenzato for Botes (58), Padro for A. Pavanello (36), Filippucci for Barbieri (58).
Not Used: Ceccato, Muccignat, Allori, Bernabo.
Saracens: Goode, Strettle, Farrell, B. Barritt, Short, Hodgson, Stringer, Stevens, Smit, Nieto, Borthwick, Botha, Brown, Saull, Wray.
Replacements: Wyles for Short (51), Spencer for Stringer (72), George for Smit (60), Gill for Nieto (45).
Not Used: Du Plessis, Smith, Melck, Taylor.
Ref: Alain Rolland (Ireland).