Jose Mourinho’s side condemned dismal Leicester to a fourth successive league defeat thanks in large part to Mkhitaryan’s dynamic contribution at the King Power Stadium.
The Armenian playmaker opened the scoring with a cool solo strike just before half-time and then teed up Juan Mata for United’s third goal after Zlatan Ibrahimovic had doubled the lead.
United’s first win in four league games extended their unbeaten run to 15 and lifted them to within two points of fourth-placed Arsenal in the race to qualify for the Champions League.
“I think we played like we normally play. We played well and tried to win,” Mourinho said.
“We are still in the same position but we are closer to the others so we keep fighting.” Just nine months after their fairytale title triumph, Leicester are firmly embroiled in a battle to avoid relegation after winning only one of their last nine league games.
Claudio Ranieri’s team are a shadow of the relentless unit that ground opponents into submission last term and have yet to score a league goal in 2017.
But, aided by Mourinho’s decision to switch Mkhitaryan into a more central role, United began to monopolise possession and finally forced Leicester goalkeeper Kasper Schmeichel into action after 35 minutes.
Ibrahimovic and Paul Pogba combined to work the ball into Rashford and the youngster’s quickly-taken low strike carried enough power to force a fine save by Schmeichel.
It was a warning Leicester failed to heed and United took the lead in the 42nd minute when Mkhitaryan punished a mistake from Robert Huth.
When Chris Smalling won a header in midfield, there should have been no danger but Huth made a rash and unsuccessful attempt to win the ball in the centre circle, giving Mkhitaryan space to nudge it past the defender and race clear of the Leicester defence before firing beyond Schmeichel.
Just 88 seconds later, Leicester shot themselves in the foot again when Antonio Valencia was allowed to run unchecked down the right before crossing towards Ibrahimovic.
Despite three Leicester defenders surrounding Ibrahimovic, the trio were all flat-footed as the United forward pounced to slot home his 20th goal of the season.
Ranieri sent on Demarai Gray and Andy King at half-time, but Leicester’s gloom deepened when Mata put the result beyond doubt in the 49th minute.
Mkhitaryan was tormenting Leicester with his clever passing and when the United playmaker deftly clipped the ball to Mata, the Spaniard was played onside by Morgan and guided his shot past Schmeichel from close-range.
Rashford and Mata couldn’t take chances to rub salt into Leicester’s wounds, but the damage had already been done.
Ranieri will hope it doesn’t prove fatal