Dempsey Crace's own goal, turning the ball into his own net from Johnny Emerson's teasing cross, sent Newcastle's second-string into the lead in their opening Group D clash at Whitley Park.
Henry Johnson's header shortly after the restart, the 18-year-old defender's first goal at Under-21 level, doubled the young Magpies' advantage before Afner Cá's quick-fire brace secured a comfortable win for the hosts, with Jack Lorentzen-Jones' late free-kick proving a mere consolation for the Hatters.
Three changes were made from Tuesday's National League Cup clash against Solihull Moors as Emerson was handed his first Under-21s start since April 2025 after missing the entirety of the previous season due to a torn anterior cruciate ligament.
United's second-string, drawn in Group D alongside Luton, Peterborough United and Nottingham Forest, went close to taking the lead through Matheos Ferreira as the 18-year-old attacking midfielder's fierce drive from the edge of the box forced Luton goalkeeper Charlie Booth into pushing the ball over his own crossbar.
Cá, who joined the Magpies' Academy last summer following the expiry of his contract from La Liga side Levante, took his turn in front of goal minutes later, racing onto Ferreira's neat pass before his powerful drive from a tight angle was turned out for a corner by Booth.
The resulting set-piece saw Newcastle clip the crossbar as Miodrag Pivaš rose from Ferreira's in-swinging corner but the Serbian defender's looping header struck the underside of the woodwork before bouncing out for a goal kick.
In the 25th minute, Newcastle took the lead through Crace's own goal. After Emerson cleverly nutmegged Darren Frimpong-Kwakye on the right flank, the Cumbrian winger drove towards goal before an inviting cross into the box was diverted into the left-hand corner by the Hatters centre-back.
The hosts doubled their advantage in the 53rd minute through Johnson as the Walbottle-born defender, who made his senior debut for Matthias Jaissle's side during a pre-season friendly against Valencia, arrived onto Emerson's free-kick from the right flank before guiding a firm header beyond Booth.
Goalkeeper Aidan Harris, who spent the first half of the 2025/26 season on loan at NIFL Premiership side Coleraine FC, was tested for the first time of the evening on the hour mark as the 19-year-old shot-stopper got down quickly to push away David Gawel's drive from distance.
Kyran Thompson, introduced from the substitutes' bench, almost netted United's third of the night as the London-born forward, a representative of England at Under-18 level, glided past Frimpong-Kwakye on the right flank before the 17-year-old's shot from an acute angle was turned out for a corner by Booth.
Newcastle grabbed a third in the 77th minute through Cá as the Guinea-Bissau striker raced onto Johnson's pass along the right wing and after dangerously cutting inside, unleashed a powerful effort into the roof of the net.
Five minutes later, Cá netted his second of the evening. After Sam Alabi's initial effort struck the base of the right-hand post, the alert African was on hand to steer the rebound into an empty net.
Newcastle's hopes of a clean sheet, though, were dashed as Lorentzen-Jones pulled a goal back for the visitors, with the Hatters skipper's emphatic free-kick from the edge of the box finding the top left-hand corner but the young Magpies comfortably saw out the contest on Tyneside.
Newcastle United Under-21s: Aidan Harris, Henry Johnson, Dylan Charlton, Miodrag Pivaš (Guy Bloomer 81), Logan Watts, Scott Bailey (c), Johnny Emerson (Kyran Thompson 62), Jayden Kouossu (Sam Alabi 69), Afner Cá, Matheos Ferreira (Alfie Seldon 69), Kyle Fitzgerald.
Subs not used: Alex Walpole, Issac Moran, Alfie Hutchison.
