Santiago Gentiletti’s goal early in the second half was the only difference between the two sides, although the Biancocelesti wasted chances to win more convincingly.
The result leaves Sampdoria clinging on to a place in Europe next season while Lazio can clinch their berth in the Champions League with a game to spare next weekend if Napoli fail to take maximum points against Cesena on Monday night.
Chances were few and far between in a tight first half with Pedro Obiang wasting the best for the hosts just before half-time.
Samuel Eto’o had an even better opportunity early in the second half, but after his shot missed the target with only Etrit Berisha to beat, the tone of the game changed.
Lazio, who had ridden their luck but were still in the game, started to pick up the reins themselves and, five minutes later, they took the lead.
Gentiletti was making his return to the Lazio team for the first time since tearing his cruciate knee ligaments at this very same venue against Genoa last September, and he marked it with a more positive memory than his last one at the Stadio Luigi Ferraris.
He may not have connected well with his shot from close range, but it bounced off the turf and into the net despite Eto’o’s attempted clearance off the line.
Samp were forced to throw men forwards to try to salvage something and this played into the hands of their visitors with Antonio Candreva’s half-volley from 20 yards out flying just wide of the left-hand post.
Filip Djordjevic saw a shot blocked as Lazio wasted one of several perilous counter-attacks, failing to put the result beyond Samp.
The hosts never looked like punishing them, though, as their blunt attack posed no threat to a well-organised Lazio rearguard, which helped sustain their push for a place in the Champions League next season, ahead of their Coppa Italia final with Juventus on Wednesday.