Glasgow fly-half Brandon Thomson missed a simple conversion with the final kick to hand Dragons a 23-22 victory at Scotstoun.
Johnny Matthews looked to have clinched four Guinness PRO14 points when he went over following a tap penalty following a lengthy onslaught which carried the game more than three minutes beyond the 80-minute mark.
But Glasgow’s celebrations proved premature as Thomson hit the post with his conversion.
Jared Rosser had notched an early try for the away team before Glasgow scored twice in four minutes through Fotu Lokotui and Sean Kennedy following the visitors’ second yellow card.
Brok Harris crossed from close range after the break for Dragons and Sam Davies kicked the visitors six points in front before the late drama.
Dragons, whose trip to Scotland had been delayed following a Covid-19 outbreak in their ranks, moved level on points with Ospreys in the top four of Conference A and still with two games in hand on fifth-placed Glasgow.
The Welsh side took the lead inside five minutes following a lineout near the halfway line. Davies offloaded to Rosser, who sprinted for the line and shrugged off two tackles, including a high one from Niko Matawalu, to touch down.
Davies added the extras before Warriors responded and Harrison Keddie was penalised for a ruck infringement and sent to the sin bin.
Warriors put the pressure on from the penalty scrum but Dragons defended well and got back on top after the teams had been evened up.
An excellent tackled from Lee Jones stopped Ashton Hewitt in the corner but the visitors had a penalty waiting for them and Davies kicked them 10 points ahead.
Warriors were handed another lifeline when Jack Dixon was sin-binned for a shoulder charge and this time the hosts took advantage.
Warriors went for the lineout drive and Lokotui went over on his first start for the club on the half-hour mark before Pete Horne converted.
Danny Wilson’s side soon went in front after Nick Grigg forced his way through and released for the supporting Kennedy to dive over. Horne put Glasgow four points ahead at the interval.
The visitors went back in front five minutes into the second half after kicking another penalty into the corner. Prop Harris went over from close range.
Horne soon levelled with a penalty but Davies put the Welsh side back in control with a long-range penalty and drop goal from similar distance.
The game further slipped away from the hosts when Jones marked his first game at Scotstoun for 22 months with a 62nd-minute yellow card for a deliberate knock-on.
Replacement Ratu Tagive was perhaps fortunate not to join his fellow winger after making a tackle in the air, and Warriors suffered another blow when replacement prop Alex Allan was wheeled off on a stretcher following a lengthy spell of treatment on the pitch.
Glasgow finally put some intense pressure on and Matthews looked to have provided the crucial moment of the game, only for Thomson to endure a kicking disaster.
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