Lecce had conceded before the 15-minute mark only once all season, but their defences were breached after just 11 seconds here.
A long ball forward, almost straight from kick-off, was taken down by Teun Koopmeiners, and he laid it off for Andrea Cambiaso to cross for Dusan Vlahovic, who got free of his markers and finished from six yards for his second goal in as many games on his injury comeback.
The hosts nearly made the perfect response two minutes later, but Michele Di Gregorio kept out Walid Cheddira’s hit from close range, only for the frantic start to continue at the other end, as Francisco Conceicao struck the post and Vlahovic forced Wladimiro Falcone into a stop with his feet, all before six minutes had been played.
The tempo soon eased off and remained that way for much of the first half, as Ylber Ramadani dragged an effort wide for the hosts, and Gleison Bremer went for the spectacular with a bicycle kick at a corner that sailed over.
Six minutes before half-time, Conceicao won possession in the Lecce half and found Vlahovic, who took his time to set himself, but fired over from the edge of the area.
The Serbian striker thought he had doubled his tally in the second half when he picked up a rebound following a Kenan Yildiz effort before needing two bites of the cherry to beat Falcone, only for VAR to rule it out for offside.
There looked to be no denying the Old Lady just before the hour mark, when the ball was worked out to Cambiaso and his low cross was turned in at the near post by Pierre Kalulu, only for VAR to spot another offside in the build-up, again against Vlahovic.
Juve still couldn’t finish the match off when a side-footer from Yildiz and Vlahovic failed to make the most of good shooting opportunities, though the same could be said for both Thorir Johann Helgason, who planted an effort straight at Di Gregorio, and Konan N’Dri, who shrugged off his marker but could only hit the side netting, on rare Giallorossi ventures forward.
But Luciano Spalletti’s side held on for a first win in three that takes them four points clear of fifth place for the time being, stretching their unbeaten run to 10 league games. Lecce, meanwhile, saw the end of their three-game run without defeat to stay four points clear of the drop zone.