- Luis Alberto (80')
Lazio have 45 points from 24 matches, one ahead of AS Roma, who play bottom-club Cremonese on Tuesday. Maurizio Sarri's side are only two points behind Internazionale and AC Milan, who both have 47. Runaway leaders Napoli are on 65.
Lazio came close to scoring in the dying seconds of the first half with striker Ciro Immobile sending an effort wide of the target.
Immobile missed another chance on the hour when, alone in the box, he sent the ball high over from close range.
Midfielder Luis Alberto secured the win when he latched on to the ball outside the box in the 80th minute and fired it to the top right corner.
The goal triggered a roar of relief from the Stadio Olimpico crowd, with Sampdoria unable to create a response before the final whistle.
The Genoa club are second-from-bottom with 11 points from 24 matches.
- Andrea Colombo