The third-placed side have now gone four games without a win and continue to lose ground on Paris Saint-Germain and Monaco in the title race.
After Rennes had started well, Lille took the lead in the 34th minute as Salomon Kalou scored his seventh league goal of the season.
Nolan Roux created the Ivorian's goal with an excellent run down the right. His low cross was scooped into the air by a Rennes defender and Kalou headed the dropping ball into the net from five yards.
Rennes, who gave new signing Ola Toivonen his debut, levelled seven minutes later as Abdoulaye Doucoure got in between two defenders to meet a left-wing cross and grab his first Ligue 1 goal of the campaign.
The second half lacked the action of the first, although both sides wasted good opportunities to move ahead.
Toivonen was replaced just after the hour mark by Nelson Oliveira, but the Portuguese was unable to inspire Rennes to a first league win on their travels since October.
