The north eastern club came into the game unbeaten and the run looked set to continue when Philippe Brunel gave them an early lead.
However, Sochaux fashioned an immediate response through Francileudo dos Santos Silva and the winner came on 23 minutes when Souleymane Diawara hit the target.
A tight game at Stade Le Beaujoire saw Nantes and Bordeaux play out a 0-0 draw, a result that was good enough to take Les Canaris to the top of the table on goal difference.
Champions Lyon suffered a surprise defeat at Guingamp.
Paul Le Guen's side were looking to build on a steady start to the season but they suffered their second defeat of the campaign at Guingamp.
Moumouni Dagano fired the home side in front on 32 minutes and Fabrizio Fuentes made the game safe with a second before the break.
The game marked Giovane Elber's debut for Lyon, following his move from Bayern Munich.
Reinaldo scored twice for Paris Saint Germain, but his feat was equalled by Habib Bamogo as Montpellier inflicted a 3-2 defeat on the capital club - with Rui Carlos Pataca netting a dramatic late winner.
Djibril Cisse and new boy Bonaventure Kalou were on target for Auxerre, who beat Rennes 2-1. Stephane N`Guema notched for the visitors.
Le Mans remain without a win after being beaten 3-0 at home by Strasbourg. Mamadou Niang was on target with goals either side of half-time for the visitors, with Danijel Ljuboja netting a late third.
Toulouse are also struggling after Corsican club Bastia grabbed a fine away victory. Florian Maurice and Ben Saada notched first-half goals for the visitors.
To view a match summary, click on a link below
Auxerre v Rennes
Guingamp v Lyon
Le Mans v Strasbourg
Montpellier v PSG
Nantes v Bordeaux
Sochaux v Lille
Toulouse v Bastia
