Mourinho, who won seven major trophies over two spells in charge of Chelsea prior to his sacking last season, tasted victory for the first time in three attempts against the Blues this season at Old Trafford on Sunday.
He had been taunted by Chelsea fans on his two trips to Stamford Bridge since being axed - a 4-0 league defeat in October followed by a 1-0 FA Cup quarter-final loss last month.
Mourinho had told Chelsea fans "Judas is still number one" after chants from his old fans in the cup defeat, having responded to them during the game by holding up three fingers to represent each of the Premier League titles he won for the club.
But this time United won 2-0 courtesy of goals early in each half from Marcus Rashford and Ander Herrera.
And Mourinho clearly relished getting one over them at Old Trafford, delighting United fans by pointing to their badge as he walked into the tunnel.