Though clear underdogs, the Rossoblu were first to threaten when Michael Folorunsho shot straight at Ivan Provedel from the edge of the penalty area in the 15th minute.
That sparked the Biancocelesti into life and they spurned two huge opportunities just before the half-hour mark. A matchwinner against Juventus in his previous home outing, Toma Basic fired over from close range after great work from Mattia Zaccagni down the left wing, before Zaccagni sent Manuel Lazzari’s low cross the wrong side of the post from a similar position.
Adam Marusic was next to go close, but his curling effort from the left corner of the box was brilliantly tipped around the post by Elia Caprile.
The visitors weathered the storm though, and in their efforts to end a 20-game winless top-flight H2H run, they almost stunned Lazio late in the half, when Sebastiano Luperto’s effort was brilliantly blocked by Mario Gila.
The return of centre-backs Luperto and Yerry Mina to the starting lineup made Cagliari more solid as they hunted just their second clean sheet of the campaign.
They could have taken the lead six minutes after half-time when Gianluca Gaetano raced through on goal, but his shot was weak and straight at Provedel.
Sensing that the game was meandering to a second successive 0-0 draw, Lazio needed to find some inspiration, and it finally came from Isaksen in the 66th minute. Bed-bound by Glandular Fever earlier this season, the Danish forward belatedly kick-started his 2025/26 campaign with a stunning solo effort, cutting inside to curl past Gila from 20 yards.
Cagliari rallied late on and Leonardo Pavoletti was inches away from turning home Matteo Prati’s fierce cross, but Lazio held on to climb five places to eighth, with a stoppage-time goal from Zaccagni sealing the deal.
Fabio Pisacane’s visitors stay 14th, but they are now without a win in six matches and remain just three points above the relegation zone.
Flashscore Man of the Match: Gustav Isaksen (Lazio)