The Aquile had a chance of their own soon after when Miroslav Klose saw his low drive from just inside the area saved by the keeper.
Alvaro Gonzalez wasted a chance to score a second midway through the first half when he was picked out at the back post by Lulic, but he placed his header wide.
Segundo Ibarbo then came close for the home side as he burst down the left wing, before he cut inside and drilled in a low strike, which was held by Marchetti.
After the break Klose had a great chance to double Lazio's lead. He burst into the box and with just the keeper to beat, he lashed a strike into the side-netting.
Keita Balde was next to threaten, but his low effort from a tight angle was pushed away by Avramov.
Mauricio Pinilla stepped up to take the spot kick, but he placed his low effort wide of the post.
Lazio made them pay for that miss immediately as Klose slipped Keita into the box, and the striker drilled a low effort past the keeper and into the back of the net.
The hosts pushed for a way back into the contest and Marchetti had to be alert to push Agim Ibraimi's long-range strike over the bar.
Cagliari finished the game with 10 men as Daniele Conti was sent off late on for picking up a second yellow card.
The visitors continued to create the better of the chances but could not add to their lead, as they saw out the match and moved up to seventh place in the Serie A table.