Needing just a point to safeguard their passage through to the knockout stages, the English heavyweights laboured against the Italian outfit and had to erase a 17-13 half-time deficit before pulling clear in the second half.
Mouritz Botha and David Strettle both touched down for Sarries and Owen Farrell added 16 points with the boot to set up a home quarter-final tie.
Mark McCall's men are now the only English side left in contention in Europe's top tournament, but will know that they will have up their game several notches when the knockout stages commence in early April.
They came into the match hoping for a bonus point win to seal top spot in Pool Five and a home quarter-final, but Treviso, unbeaten in their previous two pool games at home, were in no mood to lie down.
Farrell struck first blood for the visitors with a penalty after 10 minutes but they were rocked on their heels when Robert Barbieri dotted down for the opening try moments later, which was converted by Kris Burton.
Sarries responded impressively and hit back with a try of their own, Botha barging over from close range after the Saracens forwards had pummelled the home pack.
Farrell made no mistake with the conversion but again the visitors were found wanting in defence, and conceded a second try more or less off the restart.
Barbieri was once again instrumental, punching a massive hole in the Saracens midfield before the ball was spun wide to Tommaso Iannone, who touched down in the corner.
Burton added the conversion, and then an opportunistic drop goal to leave Treviso with a 17-10 lead 25 minutes in.
Things went from bad to worse from Saracens after they lost both Kelly Brown and Steve Borthwick to injury in quick succession, and with pool rivals Biarritz by this stage 17-0 up against the Ospreys, the wheels were in serious danger of coming off.
Farrell reduced the deficit to four points just before the break, but at half-time Saracens' cup prospects were still looking touch and go.
Thirty seconds into the second half, however, the game took a seismic swing when Strettle blocked down an attempted clearance and strolled his way over the line for a gift-wrapped try.
Farrell converted and then traded penalties with Burton to keep his side just ahead at 23-20.
Irish veteran Peter Stringer then came to the rescue for Saracens, somehow holding up Antonio Pavanello when Treviso looked certain to touch down for a third time.
Tobias Botes, meanwhile, looked to have scored a perfectly good try, but it was mysteriously overruled by stand-in referee John Carvill, who had replaced the injured Alain Rolland in the first half.
Saracens at this stage were hanging on by their finger nails, but the accuracy of Farrell allowed them to keep the scoreboard ticking over, another three-pointer on the hour mark stretching the lead to six points.
Rather than kicking on in search of the bonus point which would have guaranteed their status as third seeds, Saracens spent most of the final quarter on the back foot simply trying to protect their lead, which they just about managed to do.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.