The hosts trailed after a Pierre-Emerick Aubameyang volley in first-half stoppage-time but Souleymane Camara rescued a point with an equaliser in the 70th minute.
Montpellier, still to win at home this season and beaten 2-1 by visiting Arsenal in the Champions League in midweek, are down in 14th position in the table with five points from six games. St Etienne are up to eighth place on seven points.
St Etienne were strong at the back and Montpellier failed to get a single shot on target in the first period.
Aubameyang made amends for hitting the post two minutes earlier when he converted a Max-Alain Gradel pass from close range.
St Etienne almost made it 2-0 early in the second half when keeper Geoffrey Jourdren made a brilliant save from a Romain Hamouma header.
Both teams then created several chances before Camara missed an open goal after Anthony Mounier set him up in the 64th minute.
Camara was more ruthless six minutes later, levelling the scores after good work down the left by Remy Cabella.
Leaders Olympique Marseille will look to make it six wins from six starts this season when they entertain Evian Thonon Gaillard on Sunday (1500).
Lille, the 2011 champions, host Olympique Lyon later the same day (1900).
Among six matches on Saturday are third-placed Lorient's home game with Nice (1800) and big-spending Paris St Germain's trip to Bastia (1500).