The Londoners looked in control thanks to an own-goal from Lee Cattermole early in the second-half, but the home side rallied and equalised with just two minutes remaining through Fabio Borini.
The substitute then had a chance to win the tie just seconds before the final whistle, but the headlines will belong to Ki Sung-Yueng, who picked the perfect moment to score his first ever goal for the Black Cats in the final throws of extra time.
For Jose Mourinho, it's the end of the road in the competition that saw him lift his first piece of silverware as Chelsea manager in 2005.
Read on for player ratings and analysis for all of the Blues' players.
|John Obi Mikel||6||5|
|Kevin De Bruyne||5||7|
Chelsea were frustrated by the home side in the opening 45-minutes at the Stadium of Light and failed to create any clear-cut chances.
Andre Schurrle looked lively for the visitors, as did Willian, but most of their efforts were from distance and failed to trouble Vito Mannone in the Sunderland goal.
Quiet shifts from Lampard and Mikel didn't help, and while the Blues' back four rarely looked troubled, Samuel Eto'o failed to fire up front.
Boss Jose Mourinho had plenty of attacking options on the bench, but it was Sunderland's substitutes who would have the ultimate impact.
Mark Schwarzer: Has dealt well with everything Sunderland have thrown at him, and in truth, hasn't had a great deal to do
Cesar Azpilicueta: The Spaniard has combined useful defending with attacking intent at the Stadium of Light and has been one of Chelsea's better players
Gary Cahill: A typically solid shift from the big centre-half
David Luiz: Not one of Luiz's better halves, and he'll need to be careful after the break having picked up a yellow card
Ashley Cole: Not much in the way of an attacking threat, Cole has had a quiet half on Wearside
John Obi Mikel: Solid but unspectacular from the Nigerian international
Frank Lampard: Much like his central-midfield partner Mikel, Lampard has looked comfortable without posing any threat to the home side
Kevin De Bruyne: Not a great 45 minutes from the young Belgian with not much of an end product
Willian: A bright performance from Willian has given Chelsea promise in an attacking sense. Has showed some nice touches in and around the home side's penalty area
Andre Schurrle: Much like Willian, Schurrle's direct running and determination has caused Sunderland problems, and he's gone close on a couple of occasions
Samuel Eto'o: A trying half for Eto'o, who hasn't received the kind of service he craves up front
For long spells after the break, it looked as though Chelsea were cruising to the semi-finals of the Capital One Cup, but they overlooked Sunderland's determination.
When Frank Lampard saw the ball over the line just after the break—a goal that was later credited to Lee Cattermole—the Blues were seemingly in control, and dominated for long spells in the second-half.
But just as it looked as though fitness would see the Londoners through having made eight changes to their starting XI, the home side found another gear in the closing stages and stunned their visitors.
Jose Mourinho's side had no answer to the Black Cats' tenacity and resolve, and in the end, Ki's late winner was no more than Sunderland deserved.
Mark Schwarzer: Made a stunning save to deny Ki and couldn't be faulted for either of Sunderland's goals
Cesar Azpilicueta: After an eye-cathcing first half, the defender picked up a knock and was replaced by Michael Essien
Gary Cahill: What looked like a routine game turned into something very different for the centre-back, but he was largely solid throughout
David Luiz: A sublime, cross-field pass to Demba Ba aside, Luiz had an evening to forget on Wearside
Ashley Cole: The left-back struggled to make much of an impact before the break, and it was a similar story in the second period
John Obi Mikel: Didn't play with any real authority and fizzled out as the game wore on
Frank Lampard: Got forward well for Chelsea's goal, but didn't perform to his usual high standards
Kevin De Bruyne: The Belgian improved after the break, and went close to scoring on more than one occasion
Willian: One of Chelsea's best players on the night, the Brazilian put in a committed shift and was a real handful
Andre Schurrle: Another of Mourinho's better performers at the Stadium of Light, Schurrle was influential before being replaced by Eden Hazard
Samuel Eto'o: Not a great evening for the striker, who failed to make any impact and looked slightly off the pace