The league leaders maintained the four-point advantage they had taken into the weekend with Florian Thauvin scoring the winner on the hour mark, although Alaixys Romao's second yellow with 14 minutes left ensured a nervous finish for Marseille.
Romao hauled back Lens striker Pablo Chavarria in the 76th minute for a clear second caution of the match, but Marseille held on to claim their ninth win of the season.
Bordeaux also won on Sunday, overcoming Toulouse 2-1 to defeat their Derby de la Garonne rivals for the second time in six days and move into fourth, while Nantes drew 1-1 with Rennes.
In Marseille, the hosts opened the scoring in the 10th minute with Nicolas N'Koulou powering a header home from close range after a flick-on from a corner, but Baptiste Guillaume equalised just after the half-hour mark, finishing from near the penalty spot after Chavarria's shot was blocked.
Fifteen minutes into the second half, however, Marseille scored the decisive goal with Thauvin stabbing Andre-Pierre Gignac's cut-back into the top corner to secure victory for Marcelo Bielsa's men.
Marseille (28 points) lead reigning champions Paris Saint-Germain (24) in the standings with Lyon (23) in third, two points ahead of Bordeaux and Saint-Etienne (both 21).
Bordeaux moved ahead of Saint-Etienne on goal difference with another win against Toulouse, their second in a row after overcoming their local rivals 3-1 in the Coupe de la Ligue on Tuesday.
Marc Planus struck first for Bordeaux in the 52nd minute with a tap-in at the back post, while Diego Rolan's diving header 11 minutes later put the home side two goals ahead.
While Aleksandar Pesic dragged a goal back for Toulouse in the 68th minute, finishing from Martin Braithwaite's cross, the visitors were unable to avoid a fourth consecutive defeat in all competitions, slumping to 14th in Ligue 1.
Nantes (20 points) slipped to sixth after being held at home by 11th-placed Rennes, the home side having to come from behind to draw after conceding in just the fourth minute.
