The south-west club are now just three points behind leaders Toulon, who play at third-placed Clermont on Saturday.
Defeat for Montpellier leaves them in fourth, now six points behind Toulouse.
Toulouse's Luke McAlister and his Montpellier counterpart Buston Moyano were on decent kicking form early in the match, all the points in a 9-9 scoreline just after half an hour of play coming from their boots.
Maxime Medard crossed just before half-time to give the hosts the lead and after the break Toulouse stepped up a gear as they coasted to victory.
McAlister sent two more penalties between the sticks before Timoci Matanavou scored a try with seven minutes remaining to put a gloss on a deserved victory for Jean-Baptiste Elissalde's side.