Carson, who was often the subject of criticism whilst keeping goal for the Claret and Blue last season, gifted his former side a goal which proved to be the game's deciding factor.
Gabby Agbonlahor was the grateful recipient as his cross shot was deflected into his own net by the hapless Albion stopper.
Villa had earlier taken the lead, somewhat against the run of play, through Baggies old boy Curtis Davies.
But after half time Tony Mowbray's relegation candidates grabbed a goal via the boot of James Morrison, which made for a typically nervy finale at Villa Park.
But, Villa resisted their rivals, despite almost giving them a penalty near the end, to claim a crucial win.
With Martin Laursen and Gareth Barry back from injury, hopes were high at the start of the eagerly anticipated clash but Villa really disappointed in the opening stages.
It was West Brom who were having the lion share of possession but despite that they really failed to test Brad Friedel.
As they have done so often recently, Villa scored against the run of play and after Laursen twice had headers blocked, Barry crossed for Davies to head home.
Inevitably, the big centre back was jeered by the Baggies faithful but he silenced his critics and put his finger to his lips in celebration.
Tension
Davies was rather muted in his reaction to scoring the opener, at least being courteous to those who stringently opposed him in the away end.
Villa started to get more into the game after that and as Agbonlahor charged down the right there looked to be few options for the England frontman.
But, Carson made something out of nothing as the speedy striker fired across the box only see his former teammate deflect the ball into his own net.
Fans of the Villans may see it as just desserts for the man who cost their side a few goals during the last campaign.
After the break, Albion emerged strongly and Morrison fired in after Roman Bednar, on as sub for another Villa old boy Luke Moore, headed into his path. Game on.
Villa, knew they couldn't afford to let the lead slip and Carson made a few key saves to keep the tension levels high.
As the game drifted towards its conclusion and James Milner took the ball to the corner flag, the away side found time for one last attack and they thought they should have been awarded a penalty.
But Steve Bennett, who infamously awarded Hull a penalty against Villa two weeks ago and then changed his mind, was not to be moved as Ashley Young was adjudged to have got the ball.
For Villa it was a sweet victory in a must win game. But, for Carson and the Baggies it's more hard luck in their battle against the drop.