Ralf Rangnick was watching on in the stands, and he would have been impressed with some of what he saw in the thrilling win.
Emile Smith Rowe and Martin Odegaard got on the scoresheet for the visitors, but Bruno Fernandes’ strike and Ronaldo’s second-half brace moved United up to seventh in the table.
The visitors took the lead in bizarre fashion when Emile Smith Rowe volleyed home into an unguarded net following a clash between David De Gea and Fred.
Bruno Fernandes cancelled out the England international’s goal just before the break, converting from inside the box after a tidy assist by the Brazilian midfielder.
Ronaldo scored his first goal of the night seven minutes after the half-time interval.
Marcus Rashford set up Ronaldo who fired past Aaron Ramsdale to record his 800th career goal.
However, the Gunners hit back immediately – with Martin Odegaard picking out the bottom corner with a brilliant finish.
Though the Norwegian outdone his good work for Arsenal’s second goal by conceding a penalty.
He fouled Fred, with match referee Martin Atkinson pointing to the spot following a VAR review.
Up stepped Ronaldo who made no mistake, smashing home to bag his 801st career goal.
The Portuguese superstar wheeled away in celebration in trademark style, with his teammates even joining in on the action.
The game against Arsenal marked Michael Carrick’s final game in charge following the sacking of Ole Gunnar Solskjaer.
His three-match spell as temporary boss comes to an end with Ralf Rangnick set to take charge for the rest of the season.
The 63-year-old German watched on from the stands ahead of taking charge of his team against Crystal Palace on Sunday.
Man United’s win over Arsenal moves them to seventh place, with 21 points on the board.
As for Mikel Arteta’s side, they remain in fifth place.