Ivan Ilic netted the only goal two minutes before halftime to help Torino to their first win in five matches.
The result left Lazio two points above third-placed Juventus, who themselves were subsequently beaten by Napoli.
In a morale-boosting few days, Juventus on Thursday had their 15-point penalty suspended and also reached the Europa League semi-finals.
The return of the points - removed over transfer dealings - lifted Juventus from seventh to third in Serie A, although the club could still be punished at a later date when a new hearing is held.
Lazio struggled to find their rhythm at the Stadio Olimpico. They did have a chance in the 38th minute with a free kick from a dangerous position but Torino goalkeeper Vanja Milinkovic-Savic comfortably saved the attempt from his brother Sergej Milinkovic-Savic.
Moments later, Torino broke the deadlock, Ilic steering the ball past the diving Ivan Provedel.
Lazio sent on Italy international Ciro Immobile after the break but were unable to find an equaliser.
It was thought the forward would miss the match after he broke a rib when a tram collided with his car last weekend.
At the other end of the table, Salernitana boosted their hopes of avoiding relegation by beating Sassuolo 3-0 for a first win in six matches.
Lorenzo Pirola and Boulaye Dia netted in the first half, with Lassana Coulibaly sealing the win in the second.
The result moved Salernitana seven points above 18th-placed Hellas Verona.
Spezia have also edged above Verona after a 1-1 draw at bottom club Sampdoria.
Bruno Amione opened the scoring for the home side after 23 minutes, before Daniele Verde earned what could prove a crucial point for Spezia on the hour mark.
AAP
