Newport Gwent Dragons were celebrating their first Pro12 win since September as they held out the Ospreys at Rodney Parade.
Martyn Thomas and Lewis Robling went over for the hosts and Tommy Bowe responded.
Ospreys' starting fly-half Matthew Morgan kicked four penalties and his replacement Dan Biggar also put one over.
But Biggar also saw a last-gasp drop-goal attempt rebound off an upright.
The hosts were forced into a late change ahead of kick off with Wales hooker Lloyd Burns (illness) replaced by Steve Jones in the starting line-up.
The Ospreys made 10 changes against the league's Welsh strugglers.
Welsh lock Ian Evans returned from an ankle injury, but retained full-back Barry Davies as the only international in Ospreys' starting backline.
It was the second time in as many weeks that Dragons faced a team that made wholesale changes as Scarlets made 14 in their 10-6 win at Rodney Parade.
Injury problems led to the Dragons switching Aled Brew from wing to the centre while Tovey was at 10 following a knee injury while Wales flanker Dan Lydiate captained the Dragons for the first time.
The opening period was typically tight and occasionally feisty with the Dragons edging the half as Tovey kicked three penalties to Matthew Morgan's brace.
With ball in hand Toby Faletau was again outstanding for the hosts, offloading superbly and causing problems with his power.
But Faletau too often lacked support when space opened up in front of him.
Similarly Brew's attacking threat in midfield was difficult for the Ospreys to contend with.
However, on several occasions Brew's good work came to nothing.
The visitors had to do without Wales lock Ian Evans for 10 minutes after he was penalised at a ruck in the 12th minute.
Dragons wing Tonderai Chavhanga followed Evans to the sin-bin in the 39th minute for deliberately knocking down an Ospreys pass without any intention of catching the ball.
But the visitors also started the second period with 14 men as flanker Tom Smith illegally killed the ball after another Faletau burst.
Morgan levelled with a 45th-minute penalty but that was short-lived.
Tongan-born Wales back-row star Faletau helped set up the opening try. He took Tovey's clever pass and gave Chavhanga a run.
As the ball came back across field Will Harries put full-back Martyn Thomas over at the corner.
Visiting fly-half Morgan gave Robling a free 40-metre run to the line for the Dragons' second touchdown, the centre intercepting before sprinting away.
Tovey converted and the Ospreys responded by sending fresh legs into action, starting with a complete front-row change that saw Adam Jones, Richard Hibbard and Paul James enter the fray.
Morgan and his replacement, Biggar, each kicked a penalty before the Ospreys conjured a superb, if disputed score, for Bowe.
Centre Ashley Beck led the way as he drifted past Tovey, but there were suspicions of forward passes by Tom Isaacs and Biggar, the latter sending Bowe over.
But Biggar could not convert from the touchline and held was in despair after his drop-goal attempt failed and Darren Waters cleared into touch to end a dramatic final quarter.
Newport-Gwent Dragons: M Thomas; Harries, Brew, A Smith, Chavhanga; Tovey, W Evans; N Williams, S Jones, Buck, A Jones, Sidoli, Lydiate, L Evans, Faletau.
Replacements: Robling for A Smith (22), M Jones for Tovey (75), Bedford for W Evans (77), Buckley for S Jones (64), Way for Buck (66), Groves for A Jones (79), Waters for L Evans (72).
Not Used: Price.
Ospreys: B Davies; E Walker, Isaacs, Beck, Dirksen; Morgan, Webb; D Jones, Bennett, Jarvis, R Jones, Evans, Smith, Tipuric, Bearman.
Replacements: Bowe for E Walker (70), Biggar for Morgan (61), Fotuali'i for Webb (55), James for D Jones (50), Hibbard for Bennett (50), A Jones for Jarvis (50), J Thomas for Evans (43), Stowers for Bearman (58).
Referee: James Jones (Welsh Rugby Union)
Assistant Referees: Gwyn Morris, Wayne Davies
Citing Commissioner: Jeff Mark
TMO: Gareth Simmonds