Sale missed the opportunity to reclaim Pool One's summit as Montauban edged home 16-12 at Sapiac, claiming their debut Heineken Cup victory on Saturday.
A late penalty from Petre Mitu settled this tie at Stade de Sapiac in favour of the tournament newcomers.
Charlie Hodgson kicked four penalties to earn Sale a losing bonus point from their trip to France, but having started the day at the top of Pool One, the Guinness Premiership club are now two points behind new leaders Munster who they face next.
Victory for Montauban was reward for scoring the game's only try, a 30th-minute effort from Fiji wing Vilimoni Delasau while Sale struggled to find a scoring edge to their play amid the wind and rain in south-west France.
Sale made four changes for the trip, including the return of England trio Andrew Sheridan, Mathew Tait and Richard Wigglesworth, but it was old head Hodgson who settled their nerves with a third-minute penalty.
While Montauban may be in their first season in the Heineken Cup, they scared the life out of Munster and Clermont-Auvergne in previous games and if Sale were hoping to expose a soft underbelly to the European newcomers, they were soon proved wrong.
Montauban dominated possession as Delasau was held up over the line on 20 minutes.
Sale's defence held and Andy Tuilagi turned defence into attack with a counter-attack that almost saw Hodgson over.
The fly-half raced onto Tuilagi's interception but after kicking ahead slipped in the chase for the ball.
Delasau showed a cleaner pair of heels when he scored on the half hour.
Hodgson's pass went to ground, Montauban prop Silviu Florea got his foot to the ball and the wing kicked ahead again past Mark Cueto to score.
Rosalen converted but Hodgson had the last work of the first half to reduce the arrears to 10-6 at the break.
Hodgson paid the price for being over ambitious when he took a lineout throw to himself inside his own 22-yard line.
His pass to Tuilagi found the centre surrounded by opponents and conceded a penalty for a 13-6 home advantage.
French dissent handed Hodgson a penalty on 51 minutes that was followed by another four minutes later to bring the Sharks to within a point with half an hour to play.
Sale prop Eifion Lewis-Roberts hobbled off to a leg injury before Montauban gambled by ringing the changes, taking off both points scorers Delasau and Rosalen as the game descended into a midfield stalemate.
The game was settled three minutes form time when Sale's French lock Sebastien Chabal was penalised by Scottish official Peter Allan for not rolling away from a tackle as Montauban surged forward, handing Mitu the winner.
Pen: Rosalen 2, Mitu
Pen: Hodgson 4
Montauban: 15 Sylvain Jonnet, 14 Yohann Audrin, 13 Jean-Philippe Viard, 12 Miguel Avramovic, 11 Vilimoni Delasau, 10 Cédric Rosalen, 9 Fabrice Culinat, 8 Marc Raynaud (c), 7 Yannick Caballero, 6 Antoine Battut, , 5 Rowan Frost, 4 Mattias Rolland, 3 Silviu Florea, 2 Brice Mach, 1 Bogdan Balan.
Replacements: 16 Goderzic Shvelidze, 17 Nick Adams, 18 Karim Ghezal, 19 Matthew Clarkin, 20 Jean-Emmanuel Cassin, 21 Régis Lespinas, 22 Petre Mitu.
Sale: 15 Mathew Tait, 14 Mark Cueto, 13 Andy Tuilagi, 12 Luke McAlister,11 David Doherty, 10 Charlie Hodgson, 9 Richard Wigglesworth, 8 JM Fernandez Lobbe (c), 7 Neil Briggs, 6 Luke Abraham, 5 Dean Schofield, 4 Sebastien Chabal, 3 Eifion Roberts, 2 Marc Jones, 1 Andrew Sheridan,
Replacements: 16 Stuart Turner, 17 Lionel Faure, 18 Brent Cockbain, 19 David Tait, 20 Dwayne Peel, 21 Chris Bell, 22 Nick McLeod
Referee: Peter Allan (Scotland)
Touch judges: Rob Dickson (Scotland), Ronnie Dumma (Scotland)