Leicester survived a late onslaught to inflict just a second Premiership defeat on leaders Saracens and boost their hopes of a top-four finish.
Handre Pollard, Cameron Henderson and Mike Brown all crossed for Tigers in the opening half hour but Eroni Mawi pulled one back just before half-time.
An Alex Goode penalty and interception try by Alex Lewington put Sarries six points behind with half an hour left.
But Leicester held firm to end a run of three straight Premiership defeats.
The Tigers remain eighth in the table but are now just three points behind fourth-placed Gloucester after recording just their second win in five league outings since Richard Wigglesworth took charge in December following Steve Borthwick's appointment as England head coach.
The hosts displayed intent from the off, with inventiveness and flair creating three tries, but required resilience and defensive steel in the closing stages to secure victory - having failed to score a point in the second half at Mattioli Woods Welford Road.
Jasper Wiese set the ball rolling in the fifth minute, breaking through the middle of the Sarries defence on halfway and beating two defenders before being taken down inches from the line, and Tigers quickly spread the ball for South Africa fly-half Pollard to cross to the right of the posts.
A line break by debutant Brown and carry by Julian Montoya provided the platform for the second try six minutes later, with Henderson bustling past two tacklers to finish.
Goode, making a record-extending 350th appearance for Saracens, kicked a penalty to get his side on the scoreboard before the hosts bagged their third try.
Tigers went through the phases and then fine interplay and offloading by Chris Ashton and Jimmy Gopperth allowed former England full-back Brown, who joined on a short-term deal last month, to cut in from the right wing and Pollard added his third conversion.
After Ashton was denied a try in the corner by a fine tackle by Lewington, a long-range Pollard penalty stretched the lead to 21 points at 24-3.
Yet Saracens got back in the game just before the break as their forwards took control and Fijian prop Mawi went over from a pick-and-go.
The visitors continued their momentum after the restart, with Rotimi Segun held up over the line before Goode slotted his second penalty from just outside the 22.
Lewington then pounced on a loose pass to race from midway inside his own half and score, but Goode missed the resulting conversion.
The game then became a case of Saracens attack against Leicester defence, with Theo Dan held up and the Tigers managing to withstand the pressure with a number of last-ditch tackles to deny Sarries another remarkable comeback.
Leicester: Brown; Ashton, Scott, Gopperth, Potter; Pollard, Youngs; West, Montoya (capt), Heyes, Martin, Henderson, Liebenberg, Cracknell, Wiese.
Replacements: Clare, Van Wyk, Hurd, Snyman, Reffell, Edwards, Atkinson, Simmons.
Saracens: Maitland; Segun, Lozowski, Tompkins, Lewington; Goode (capt), Davies; Mawi, Pifeleti, Riccioni, Ellis, Tizard, Christie, Wray, B Vunipola.
Replacements: Dan, Hislop, Judge, Boon, Knight, Van Zyl, Hartley, Harris.
Referee: Tom Foley.