Trailing 3-1 from last month’s first leg at Emirates Stadium, Olivier Giroud gave the north London side hope of a famous comeback when he finished high into the net in the 36th minute at Stade Louis II.
Substitute Aaron Ramsey then drilled home from inside the box in the 79th minute but Arsenal were unable to find the crucial third goal.
Monaco deserve it and that’s absolutely fine
Gunners captain Mertesacker admitted that the damage was done in the first leg of the last 16 tie as Monaco went through on away goals after a 3-3 draw on aggregate.
Speaking to ITV Sport after the game, Mertesacker said: “The best team went through. Monaco deserved it because they played much better in the first leg.
“We played well today but it was a massive deficit, and it wasn’t enough tonight. We came here and tried absolutely everything, and when you look at the game we could have scored more than two.
“Monaco deserve it and that’s absolutely fine. They caused a lot of problems away from home. We have to admit that we regret the first game.
“But if we continue to play like that we’ll do well in the FA Cup and the league. But play as badly as we did in the first game and you’re out of the Champions League. Monaco deserved it.”
Arsenal, who have lost at the last 16 stage of Europe’s elite club competition for the last five years, take on Newcastle United in the Premier League this weekend.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news