First half goals from Casemiro and a deflected Marcus Rashford strike were all the Red Devils required to end their six-year trophy drought.
At a raucous Wembley, Newcastle started brightly but their lack of firepower upfront was telling.
At the opposite end United had an in-form Rashford to rely on but needed a setpiece to open the scores in the 33rd minute.
Luke Shaw swang in a wonderful setpiece and Casemiro was on hand to divert his header past Newcastle debutant Loris Karius, who was in goal in place of the suspended Nick Pope.
Six minutes later Wout Weghorst, slid Rashford through and the Englishman's strike was deflected past Karius by Sven Botman.
For Manchester United, it is their first trophy since the Europa League in 2017 under Jose Mourinho while Newcastle's own wait for silverware stretches to 54 years.
Speaking to Sky Sports after the game, Manchester United manager Erik Ten Hag said: "Yet again the right spirit, we have a very good spirit to fight and give everything. It was not always the best football but it was effective.
"First you have to win the first one and that is what we did today. You can get inspiration from this and more confidence that we can do it.
"We are still at the start of restoring Manchester United to where they belong and that is to be winning trophies. This is the first one.
"They [the players] are good and connected and they also challenge each other and it is a good dressing room and in the moment it is difficult they help each other out. It is the best a manager can get.
"I just want to win. We invest from the start with the staff. They did an incredible good job with the players. The staff and players are together. There was a hunger and desire for trophies because Man Utd stands for trophies.
"Raphael Varane, Casemiro and David de Gea know how to win trophies and you need such lads on the pitch to point the team. They have the winning attitude they have to bring it in the dressing room, in difficult situations and that is what they have done."
