The beginning of the day was all about David Moyes, who was making his first return to Old Trafford since he was sacked over two years ago.
His team started well until Daley Blind rounded off a wonderful team move to give Jose Mourinho's side the lead at half-time.
Zlatan Ibrahimovic and Henrikh Mkhitaryan added two more goals for United in the second half before Fabio Borini scored a consolation goal late on for the visitors but in the end United ran our deserved winners.
Defensive visitors frustrated the hosts early on
The game took a while to get going early on as the visitors set up to frustrate the hosts and it worked well for most of the half.
The first decent chance of the game went the way of the Black Cats when Patrick Van Aanholt forced David de Gea into a good save from a free kick from the edge of the box.
United though responded well after that and almost took the lead when Paul Pogba hit a curling shot from the edge of the box but unfortunately for the midfielder, it hit the post and went wide.
Apart from that though Sunderland were comfortable at the back and they should have went in front when Jermain Defoe played a great cross into the box, which fell to Victor Anichebe at the back post, but De Gea made himself big and made a crucial stop for the hosts.
Blind gave United a crucial half-time lead
That chance seemed to wake United up and they managed to get the crucial first goal. A wonderful team move saw Ibrahimovic lay the ball to Blind in the box and the left back hit the shot first time into the back of the net.
The confidence team lifted after that as Juan Mata and Pogba forced Jordan Pickford into making good saves which meant it was only the one goal at half time.
United dominate but missed chances at the beginning of the second half
The hosts came out at the start of the second half on the front foot and they should have doubled the lead on a couple of occasions. The first chance came when Pogba headed a cross over the bar when he was unmarked in the box. The second chance came when Ibrahimovic saw a shot well saved by Pickford after Mkhitaryan, who came on as a second half substitute, played the striker through.
Ibrahimovic and Mkhitaryan score late on to ensure a fourth successive win for the Red Devils
They shouldn't have worried though as finally the second goal did come when Dider N'Dong gave the ball away in his own half to Pogba, who played a lovely through pass to Ibrahimovic, who made no mistake by confidently curling the ball into the back of the net.
United managed to get a third goal not long after when an Ibrahimovic cross was brilliantly finished by Mkhitaryan, who scored with a lovely back heel flick into the top corner of the net.
Just as it looked like the hosts were going to see the game out with a clean sheet, Borini had other ideas as he smashed home a 30 yard volley into the top corner of the net.
It was only a consolation goal though for the visitors as United made it four wins in a row in the Premier League.