Neil McCann's sweet 29th-minute finish handed John Hughes' side a deserved interval lead, but First Division side Queens rallied after the break to draw level through Stewart Kean.
However, Falkirk - semi-finalists in this competition in 2007 - regrouped and ex-Aberdeen marksman Lovell pounced to cap his first start for his new club with the winning goal 17 minutes from time.
Queens, boosted by the return of Steve Tosh following suspension, almost made the perfect start inside two minutes.
However, left-back Bob Harris saw his 18-yard free-kick deflected over after McCann had been sloppy in gifting the visitors possession.
Moments after Craig Barr was cautioned for a robust challenge on Graham Barrett, the Bairns replied when Lovell laid the ball back for McCann, who clipped a left-footed effort just too high.
Gordon Chisholm's charges were already beginning to close ranks and frustrate, but a neat Falkirk move almost came to fruition after 17 minutes only for Barrett to skew wide from Michael Higdon's chest-down.
Misplaced passes were hindering the hosts' effort in the final third and Kevin McBride tried to take matters into his own hands, only to rifle a 30-yard drive wide of target.
But the craved-for Falkirk opener arrived just seconds from the half-hour mark. Following a number of passes in midfield, Jackie McNamara collected the ball close to the right touchline.
The former Scotland international's cross drifted over the head of Higdon but McCann wrapped his foot around a left-foot volley that flew past the helpless Cameron Bell.
The Dumfries side had barely been seen as an attacking force, yet they passed up a glorious opportunity in the 37th-minute after Tosh's quick free-kick caught the hosts cold and Jim Thomson nodded his free header over.
Queens, last May's Scottish Cup finalists, started the second period in far more positive fashion, with Stephen Dobbie soon curling just past.
It was a warning Falkirk failed to heed as Chisholm's men equalised a minute before the hour mark.
Scott Robertson's ball down the right was simply not dealt with by the Bairns and Kean took full advantage to lift the ball over Robert Olejnik.
Queens had finally sprung to life and Hughes sought to stem the tide by throwing on Patrick Cregg and Burton O'Brien.
The tactic immediately paid dividend, as Cregg released Lovell, who sprung the offside to race in on goal, round Bell and slot home.