Carew had scored a late equaliser in Saturday's 2-2 draw with Wolves and he again came to the rescue after Fraizer Campbell had given the Black Cats a 22nd-minute lead.
The Norwegian international netted his 14th goal of the season - and his sixth in the last five games - to ensure Villa remain unbeaten in the Premier League in 2010.
But that will be scant consolation to O'Neill and his players in their bid to break into the top four and they have now drawn seven of their last 10 league games.
Villa had enough opportunities to have claimed all three points and Ashley Young again posed plenty of questions with his crosses into the box.
But Black Cats keeper Craig Gordon maintained his recent impressive form to help his side extend their unbeaten run to five games from which they have claimed nine points.
And Sunderland also had their own chances to have registered a first away victory since the opening day of the season.
But they are now looking virtually gauranteed of top-flight football for another campaign.
Villa were the first to threaten after five minutes.
Young found himself in space to the right of the Black Cats penalty area and his fierce dipping shot was saved by the legs of Gordon.
Young won the first corner of the game and, from Stewart Downing's centre, Gordon again did well to block a powerful header from Villa central defender James Collins.
Villa looked lively in the early stages and a dangerous ball from Young only just eluded the lunge of Emile Heskey inside the six-yard box.
In a rare Sunderland attack, leading scorer Darren Bent had the ball in the net but the flag was already up for offisde.
The home side were forced into a change after 14 minutes when Heskey limped out of the action to be replaced by youngster Nathan Delfouneso after appearing to over stretch.
It was a worrying sight for Villa with top scorer Gabriel Agbonlahor already sidelined with a foot injury.
Villa continued to dominate and Collins headed an inswinging Young free-kick wide at the far post after Alan Hutton had brought down Delfouneso.
But after 22 minutes, Villa were rocked on their heels when Campbell put the visitors in front with his third goal in the last four matches.
Kieran Richardson was the creator with a perfectly weighted pass which allowed Campbell to beat the offside trap before lofting his shot wide of Brad Friedel.
Villa tried to retaliate and Richardson produced a timely tackle on Milner as he prepared to shoot 20 yards out.
Then after half an hour the in-form Carew brought Villa back on level terms.
Milner picked out the run of Young and his low skidding cross was turned home by the former Lyon player just inside the six-yard box.
It brought his goal tally to six in the last five games and was no more than Villa deserved on the balance of play.
Campbell had a good chance to restore Sunderland's lead a minute before the interval.
He seized on to a flick on from Bent after getting in front of Richard Dunne but failed to make proper contact on his shot.
John Mensah wasted a golden chance to restore Sunderland's lead after the interval.
Henderson played a short free-kick to Richardson and his floated cross found Mensah completely unmarked six yards out but he headed wide.
The game was flowing from end to end and Gordon fingertipped a curling effort from Carew around the post although referee Mike Dean awarded a goasl-kick.
Carew showed tremendous pace and power to surge into the Sunderland area but lost control at the vital moment.
Sunderland defender Mensah limped off after 71 minutes and was replaced by Paulo Da Silva.
Carew continued to pose problems and glanced a header wide from a Downing centre but Villa were unable to find a winner.
And Friedel had to be alert to turn a low effort from Campbell around the post after Richard Dunne was dispossessed by Bent.