Andy Delort scored the opener at the Stade Pierre Mauroy mid-way through the first half.
Jordan Ferri's slick first time pass sent Gaetan Laborde scampering down the right wing and Delort headed his cross past Lille goalkeeper Mike Maignan.
It was only the 20th goal conceded by Christophe Galtier’s men this season in Ligue 1.
Reward
Lille battled hard for an equaliser but Montpellier held firm.
However, with five minutes remaining the hosts' pressure paid dividends.
Luiz Araujo, a 77th minute replacement for Jonathan Bamba, beat Montpellier goalkeeper Jonas Omlin after being set up by Mehmet Zeki Celik.
The draw will at least keep Lille in pole position.
Paris Saint-Germain, who host Saint-Etienne on Sunday, can close the gap to one point if they win at the Parc des Princes.
