Mallik Wilks scored a fifth-minute opener, and it took Leeds until the 93rd-minute to find an equaliser through Ezgjan Alioski’s scrappy finish.
Former Leeds forward Wilks, returning to Elland Road for the first time since his 2019 exit, linked up with George Honeyman and Keane Lewis-Potter before his deflected shot found the back of the net.
Hull went on to dominate proceedings and missed multiple chances to put the game beyond the Whites, but Alioski thought he had saved his side’s blushes after the Tigers failed to clear their lines from a Barry Douglas corner.
The North Macedonian international missed Leeds’ second penalty of the shootout, but Leeds academy product Lewie Coyle saw his shot saved by Kiko Casilla to keep the scores level in the shootout.
Leeds were deservedly knocked out after Jamie Shackleton’s miss was followed up by Alfie Jones’ winner, booking Hull a trip to London to face West Ham United in the third round.
Grant McCann’s side should have wrapped up the affair within 90-minutes, as a Leeds side much changed from the 4-3 defeat to Liverpool last weekend failed to make their possession count.
The Peacocks lacked end product and struggled to create opportunities in the final third, with Robbie Gotts’ tame 89th-minute effort his side’s first on goal in the entire match.
Alioski missed the Peacocks’ greatest opportunity minutes before half-time, as he lashed the ball over from inside the area after full debutant Rodrigo Moreno’s shot was deflected into his path.
In stark contrast, Hull could have been two or three goals up at the interval; at the half-hour mark, Wilks threatened to score his second after charging unopposed towards goal, before unleashing a powerful effort from outside the box that Casilla managed to block.
Fellow Leeds youth product Daniel Batty generated another big chance for the visitors, as his long ball from deep was held down nicely by Keane Lewis-Potter, who cut inside and curled an effort just past the far post from the edge of the area.
A first half to forget for Leeds ended after Jones headed just wide from Callum Elder’s free kick, but remained at 1-0 largely thanks to a few solid saves from Casilla.
Leeds momentarily took a firmer grasp on affairs in the second half, with Ian Poveda looking particularly dangerous on his tricky runs through the Hull defence, but the Whites continued to lack final product.
Hull soon retook control, though, and Casilla was forced into a flying save by Greg Doherty’s shot from distance. Ten minutes later, Doherty forced the Spaniard into another save, with his parry leading to James Scott heading George Honeyman’s cross just wide.
The visitors, captained by former Leeds full-back Lewie Coyle, continued to search for a two-goal cushion in the latter stages of the match, with Billy Chadwick’s shot from inside the area blocked.
Scott was next to have another effort on goal; the 20-year-old was played through on goal but could not beat Casilla one on one.
Leeds’ first shot on target came in the dying moments of the game, as substitute Gotts curled a tame effort into the arms of the previously untested Matt Ingram prior to Alioski’s equaliser.
The match will at least be remembered fondly by Charlie Cresswell; the 17-year-old was one of the better players on his debut, demonstrating a good range of passing while proving strong in the tackle.
But the inexperienced partnership of Cresswell and Oliver Casey produced some shaky moments as Wilks terrorised Leeds in the first half.
The introduction of Pascal Struijk in defensive midfield did little to help Leeds take firm control of the game, subsequently leading to a lack of service for full debutant Rodrigo.
Leeds return to Premier League action with a match at home to Fulham this Saturday.