Thanks to Casemiro's header and Sven Botman's own goal, Erik ten Hag's team took control by halftime, and despite Newcastle's pressure in the second half, United held on to secure a 2-0 victory.
This win was the first silverware for United since 2017 and the celebrations could be the start of a golden era for the club, with United still in contention on three other fronts.
Ten Hag's transformative first season as United's manager has led the team out of one of the darkest periods in the club's history.
Even United co-chairman Avram Glazer, who had been considering selling the club, might reconsider after viewing the team's impressive performance.
Although Newcastle failed to win their first major trophy since the 1969 Inter-Cities Fairs Cup, they can expect to feature in more showpiece occasions soon.
Newcastle has been revitalized since their takeover by a Saudi-funded consortium, and with Eddie Howe as their boss, they are now fifth in the Premier League.
Newcastle's fanatical "Toon Army" turned Wembley into a roiling sea of black and white, belting out songs of praise for their heroes well over an hour before kick-off.
However, United spoiled the party in a composed style, with their commanding performance proving too much for the Magpies.
Although this League Cup triumph is no guarantee of future success, the steely Ten Hag appears more than capable of thriving in the unrelenting Old Trafford spotlight.
And if this success is any indication, the Ten Hag era at United is built on far stronger foundations than the team's previous League Cup triumph.