A lively start saw both teams squander chances in the opening few minutes, with Alieu Fadera striking just wide after the ball rebounded to him in the box, while Gustav Isaksen fired over at the other end.
Elia Caprile was the first goalkeeper called into action when he saved Davide Frattesi, then produced a better stop to deny Mattia Zaccagni from the edge of the box.
Despite Lazio’s probing, Cagliari took the lead through M’Bala Nzola, who scored his second goal in as many appearances by sliding in Fadera’s cross at the near post.
It was the first time Lazio had been behind since matchday three, but they quickly levelled when Tijjani Noslin found Isaksen, who superbly swept his fourth goal in five games into the top corner.
Cagliari almost responded through Jacopo Fazzini, who dragged his effort just wide, but the hosts preserved their record of being the only Serie A side yet to trail at half-time this season (W5, D5).
Determined to cause an upset, Cagliari came out fighting in the second half and almost went in front again when Jose Pedro could not get the clean contact he wanted from a corner as the ball flicked off his shoulder and over the bar.
Christos Mandas then got behind Michel Adopo’s deflected strike from range, but the visitors could not make their pressure count.
Lazio were still a threat down the other end too, and Kenneth Taylor’s free-kick troubled Caprile, who parried it away. After a lovely passing move, the midfielder then side-footed inches wide as the Biancocelesti continued to probe.
After their arch-rivals Roma beat Cagliari on Tuesday, Lazio were desperate to do the same, and it took until the 83rd minute to find the breakthrough they craved.
Two substitutes combined as Alfonso Pedraza found Andrea Pinamonti in the box, and he headed home to send the Biancocelesti wild.
To pile on Cagliari’s misery, Adam Obert then fouled Isaksen for a second yellow and subsequent red, as the visitors lose a fourth successive match.
Lazio remain unbeaten with a ninth win in 10 league games (D1), and establish themselves as genuine title contenders.
Flashscore Man of the Match: Andrea Pinamonti (Lazio)