Daniele Dessena's goal late in the second half ended the Biancocelesti's three match winning streak and consigned them to a seventh place finish behind city rivals AS Roma. The Sardinians meanwhile finish in an impressive 11th position.
Ongoing problems with Cagliari's IS Arenas home meant this game was played in Trieste. Former Lazio coach Edy Reja dropped by to watch the game from the stands.
Cagliari were without injured defenders Lorenzo Ariaudo, Francesco Pisano and Nicola Murru, while Michael Agazzi and Marco Sau were surprisingly rested. Libor Kozak got a rare start for Lazio, who were without injured pair Stefan Radu and Hernanes.
The hosts dominated the first half. Thiago Ribeiro saw an effort turned around the post by Federico Marchetti. Danilo Avelar ballooned over and Kozak headed a Senad Lulic cross wide at the other end. Daniele Conti threaded through for Victor Ibarbo, only for the frontman to be thwarted by an alert Marchetti.
Just past the half hour, Antonio Candreva sent a free kick over from a promising position. In stoppage time, Avelar cut inside the Lazio box and his shot hit the crossbar en route to going out of play.
The visitors enjoyed a brief spell of dominance in the second half. Candreva volleyed Cristian Ledesma's cross towards the near post, but Vlada Avramov got down to smother the ball. Sergio Floccari came on and headed wide from six yards, before Lorik Cana tried his luck from 35 yards, which saw Avramov collide with the post as he scrambled back to make the save.
Cagliari hit the front from a set piece with 15 minutes left to play. Sau whipped the ball into the box for Dessena to leap highest and head in just yards from goal. Floccari saw a goalline scramble come to nothing as Lazio failed to find an equaliser. All eyes will be on Rome for next weekend's explosive Derby della Capitale Coppa final.
Cagliari: Avramov, Avelar, Astori, Rossettini, Dessena, Nainggolan, Conti, Eriksson, Thiago Ribeiro, (Cossu 69) Ibarbo, (Nene 86) Pinilla (Sau 73)
Lazio: Marchetti, Biava, (Ederson 77) Cana, Dias, Konko, (Gonzalez 71) Onazi, Ledesma, Lulic, Candreva, Kozak, (Floccari 57) Klose
Goals: Dessena 75 (C)