The Argentine's well-taken first-half goal sealed all three points for Laurent Blanc's side, which missed a number of chances to make the scoreline more impressive.
Rennes had beaten PSG 2-1 on each of its last two visits to the Parc des Princes but, although the host was not clinical, Laurent Blanc's men ultimately strolled to victory.
The away side held its own early and afforded PSG few sights of goal, but the champion's superior quality showed just before the half-hour mark, as Lavezzi capped off a delightful move which involved Zlatan Ibrahimovic, Adrien Rabiot and Javier Pastore.
Rennes – which had not won any of its previous six in all competitions – went close to hitting back through Paul-Georges Ntep a few moments later, with Salvatore Sirigu called into action.
Edinson Cavani missed two opportunities to double PSG's lead at the beginning of the second half and was jeered by sections of PSG fans when substituted.
The host failed to add to its lead in the latter stages, but regardless edged back to within a point of Lyon – which faces Monaco on Sunday – and goes into its Coupe de La Ligue semifinal at Lille on the back of five successive victories across all competitions.
Blanc seemingly had one eye on Wednesday's clash, as Blaise Matuidi and Marco Verratti were rested from the start, while Thiago Motta's absence through suspension left PSG struggling for fluency in midfield.
The host's patience eventually paid off, though, and it broke the deadlock in stylish fashion in the 29th minute.
Ibrahimovic carried the ball forward and combined with Pastore, who, after nudging it on to Rabiot, collected a chipped return pass inside the area and squared to Lavezzi for an easy finish at the end of a free-flowing move.
Rennes went close to restoring parity five minutes later, but Sirigu made a crucial save to deny Ntep after the forward pounced on Pastore's dreadful back-pass attempt.
PSG started the second period with renewed urgency and Cavani went close to adding his name to the score sheet twice in quick succession.
The Uruguayan first failed to connect with Marquinhos' teasing right-wing delivery, before seeing a controlled effort brilliantly tipped around the post by Benoit Costil following Lavezzi's defence-splitting pass.
Cavani then appeared to exchange words with Blanc upon his substitution in the 69th minute, as whistles rolled down from the stands, before Sirigu kept PSG ahead shortly after with an easy save to deny Christian Bruls.
Rennes enjoyed some pressure toward the end, but it ultimately proved to be too late as PSG claimed a routine victory, putting the pressure back on fellow title challengers Lyon and Marseille.