Full-back Adrian Cashmore kicked 16 points as the Ospreys beat Clermont Auvergne in Swansea's Liberty Stadium.
HEINEKEN CUP POOL THREE
Ospreys: (20) 26:
Tries: Mustoe, Terblanche.
Cons: Cashmore 2.
Pens: Cashmore 4.
Clermont: (7) 12:
Tries: Garcia, Vermeulen.
Both sides had only pride to play for as neither side could qualify for the Heineken Cup quarter-finals.
But the Ospreys had the satisfaction of climbing off the foot of Pool Three as Richard Mustoe and Stefan Terblanche crossed for welcome tries.
Clermont hit back through Pierre-Manuel Garcia and Elvis Vermeulen tries, but Craig McMullen managed one conversion.
McMullen started at fly-half for the French visitors because of an injury to their Wales and Lions star Stephen Jones.
Although Jones missed this match against his countrymen, he is expected to be fit for Clermont's final group match next week at home to Leicester.
Two Cashmore penalties gave the Ospreys an early lead, before an error by McMullen handed the Welsh side their opening try.
The Clermont fly-half spilled a ball in his own half; Ospreys number eight Jonathan Thomas hacked on and wing Mustoe picked up and scored under the posts.
That try was cancelled out only five minutes later when McMullen broke through into the 22, and Anthony Floch put Garcia in under the sticks.
Ospreys produced the perfect riposte when Cashmore put Terblanche on a great angled run to the line to give the home side a 20-7 interval lead.
Four minutes into the second half, Cashmore planted his third penalty to give his side a 16-point cushion.
Ospreys suffered a setback when outside-half Shaun Connor was handed a yellow card following a scrap with Clermont wing Breyton Paulse.
But both sides found themselves a man short, after Gonzalo Longo found himself in the cooler for throwing a punch.
However, Clermont upped their forward effort, with number eight Vermeulen squeezing over from a maul.
But the Ospreys were not fazed and managed to keep the Frenchmen at bay for the rest of the match.
Ospreys made their way back up the field and were rewarded with a fourth penalty for the in-form Cashmore.
It was their second home win against a French side in the group, having beated Stade Francais who they travel to next week hoping to achieve a rare double over the Paris side.
Ospreys coach Lyn Jones:
"It was a tough game but with the run of four defeats we've had recently, we badly needed a win.
"I was impressed with some of the yougsters today, as we had so many players out for various reasons.
"Hopefully this will be the kick-start we need, although I'm under no illusions how hard a task it will be next week out in France against Stade Francais."
Ospreys: Adrian Cashmore; Stefan Terblanche, Sonny Parker, Leigh Davies, Richard Mustoe; Shaun Connor, Jason Spice; Duncan Jones (capt), Huw Bennett, Andrew Millward, Andrew Newman, Lyndon Bateman, Jonathan Thomas, Richard Pugh, James Bater.
Replacements: Andrew Bishop for Davies (66), Matthew Jones for Connor (84), Richard Rees for Spice (35), Richard Hibbard for Bennett (63), Adam Jones for Millward (54), Steve Tandy for Pugh (20). Not Used: Lee Beech.
Clermont Auvergne: Anthony Floch; Breyton Paulse, Pierre-Manuel Garcia, Tony Marsh, Julien Malzieu; Craig McMullen, Jerome Moreau; Laurent Emmanuelli, Mario Ledesma, Martin Scelzo, Jamie Cudmore, Thibaut Privat, Gonzalo Longo-Elia, Sam Broomhall, Elvis Vermeulen.
Replacements: Raphael Chanal for Floch (68), Davit Zirakashvili for Emmanuelli (66), Brice Miguel for Ledesma (62), Alexandre Bastin for Scelzo (57), Loic Jacquet for Privat (62), Emmanuel Etien for Longo-Elia (73). Not Used: Gonzalo Canale.
Referee: Carlo Damasco (Italy).