The opening 10 minutes were anything but cagey, with Joelinton blazing his strike over the crossbar and Martin Dúbravka smothering Kai Havertz’s effort after Gabriel Martinelli and William Saliba had seen a shot apiece blocked.
The opportunities initially kept coming but Jurriën Timber headed over from a Declan Rice corner delivery and Sandro Tonali couldn’t keep his effort down after Lewis Hall’s shot was denied.
Newcastle pressed relentlessly and the Gunners tried to work a way through them, eventually doing so just before the half-hour as Martinelli sprinted away from Sven Botman but crashed his strike against the post.
That moment gave the hosts an extra spark and Botman was soon forced to launch his body into the line of Havertz’s attempt.
The Emirates was left stunned in the 37th minute, though, as Botman won the header from Dúbravka’s long free-kick and Jacob Murphy teed up Alexander Isak for the talismanic striker to clinically score a memorable 50th goal in his 89th Newcastle appearance.
Arsenal were denied a swift response as Dúbravka rushed out to stop Gabriel Magalhães’ venomous strike before the break and their deficit was doubled within six minutes of the restart.
David Raya got down to stop Isak’s attempt but could only palm the ball into Anthony Gordon’s path for the winger to convert from close range.
Havertz then completely mistimed his header from a deflected Leandro Trossard cross, Saliba headed wide from another Rice corner, and Martinelli’s improvised hit fizzed off-target as the Gunners’ misery continued.
The hosts continued to apply waves of pressure, but Jorginho fired over as Newcastle stood firm to maintain a two-goal margin in what is now their seventh consecutive win across all competitions, strengthening their hopes of reaching a second EFL Cup final in three seasons.
They also ended Arsenal’s 13-match unbeaten run and gave the Gunners an uphill battle to reach the final of this competition for the first time since 2018.