Carroll — the club’s much-maligned £35 million record signing — glanced in a Craig Bellamy free-kick in the 87th minute to keep Liverpool on course for a domestic cup double.
It was the second time in five days that Carroll had come to Liverpool’s rescue after scoring an injury-time winner in the Premier League victory over Blackburn in midweek.
More importantly the goal ensured Liverpool have the opportunity to finish a disappointing season on a high in next month’s final where they will face the winner of Sunday’s last-four clash between Tottenham and Chelsea.
Carroll’s decisive strike came after Liverpool had fought back to level through Luis Suarez on 62 minutes following Nikica Jelavic’s opener for Everton.
Liverpool had started well, with Glen Johnson surging forward menacingly after only three minutes to release Carroll.
The pony-tailed striker cut back deftly to Jay Spearing but the young midfielder should have done better than a shot which flew harmlessly over.
Liverpool chances thereafter were few and far between, and while Kenny Dalglish’s side often advanced into good attacking positions their forays invariably fizzled out because of poor play in the final third.
Everton meanwhile looked comfortable throughout the first period, mopping up Liverpool’s attacks with ease and probing for openings.
On 24 minutes Liverpool were made to pay for their lacklustre opening as Jelavic pounced for his sixth goal since signing from Rangers in January.
Daniel Agger dithered over a clearance inside the area before Jamie Carragher attempted to scramble the ball to safety.
Carragher’s intervention cannoned back off Tim Cahill and into the path of Jelavic who finished coolly to send the blue half of Wembley into raptures.
The anticipated response from Liverpool never came however and they struggled to test Everton through the remainder of the half, with an off-target long-range Steven Gerrard effort on 37 minutes their only attempt on goal.
It was a different story after the break however as Liverpool started with far more purpose.
Indeed they should have levelled on 47 minutes only for Carroll to send a downward header yards wide after a perfect cross from Stewart Downing.
Carroll buried his head in his shirt while Dalglish clutched his hands to his face in disbelief — a response mirrored up in the stands by Liverpool’s legendary No.9 from the 1980s Ian Rush.
But just when it seemed Everton had withstood the early onslaught, Liverpool drew level on 62 mintues. Sylvain Distin underhit his backpass to Tim Howard and Suarez raced through on goal before poking his finish under the American keeper.
The relief coursed through Liverpool’s massed ranks of fans and they looked by far the likeliest side to score for the remainder of the game.
Carroll should have done better but dragged a low shot wide on 78 minutes while at the other end Jelavic briefly raised Everton hopes when his shot flew into the side netting.
Then with extra-time looming Everton substitute brought down Gerrard wide on the left flank.
Liverpool substitute Bellamy, who had only been on the pitch a matter of minutes, chipped in a perfectly flighted effort and Carroll outjumped Jelavic and Marouane Fellaini to glance home.