Goals from Will Keane and Andreas Pereira in the second half settled the game for the Reds who came through the game with ease.
The game was special for a few players with Luke Shaw making his comeback for United after 10 months out with injury, while Henrikh Mkhitaryan and Eric Bailly made their United debuts.
United dominated the first half but failed to get the breakthrough
United began the game on the front foot and kept possession well, with Wigan failing to get out of their own half, but they failed to create any meaningful chances in the first 15 minutes. Mkhitaryan started the game very well and looked right at home in a United shirt, with a lot of nice touches and link up play between the other players.
United, though, did finally create a chance and they should have scored, when Mkhitaryan was played in on the right-hand side of the box. The attacking midfielder then laid the ball across the box into the path of Memphis but somehow the winger put his shot wide instead of putting the ball into the net.
Mkhitaryan was next to go close for the Reds when Jesse Lingard played a great ball into the area but the Armenian fired his effort over the bar when he should have hit the target. United continued to press for the breakthrough right until the end of the half but failed to do so with Wigan defending really well to go in at half-time goalless.
Keane and Pereira score early in the second half as United stroll to a 2-0 win
Mourinho made seven changes at half-time and it had instant success as Keane scored the opener four minutes into the second half. The goal came from a terrible mistake from Wigan goalkeeper Jussi Jaaskelainen, who cleared the ball straight to Juan Mata, and the Spaniard played the ball across to Keane who tapped the ball into an empty net.
Keane almost made it two soon after but he put his shot just wide of the goal. The chance came from Mata who spun the defence beautifully and then played a great ball to Ashley Young who crossed the ball to Keane but he couldn't put the ball in the net.
The second goal did come when Pereira hit a lovely curling shot from just inside the box into the top corner of the net. The goal was something that was practised of the training ground as Mata played the free kick back for Ander Herrera to strike, but it was blocked; then it went into Periera's path and the midfielder smashed the ball home.
Wigan were unable to create anything after United went two goals up and the visitors kept the ball really well and were comfortable throughout the second half.
The second half ended with a very satisfactory win for Mourinho in his first game in charge with United being never really challenged through the game but there will be tougher games to come in the next couple of weeks.