The Bulgarian scored two second-half goals and then set up Geoffrey Kondogbia for the game-clinching third before Lucas Ocampos' volley added some late gloss
Claudio Ranieri's men knew that nothing other than victory would gift the championship to PSG but they performed poorly in the opening 45 minutes.
However, Berbatov belatedly made the breakthrough early in the second half with a clever header before doubling the visitors' advantage with 16 minutes ago.
Gadji Tallo set up a frantic finale with an emphatic finish moment later but Monaco sealed a fourth straight Ligue 1 win when Berbatov teed up Geoffrey Kondogbia for a third goal just two minutes from time before Lucas Ocampos put the finishing touches on an ultimately facile win in the dying seconds.
Monaco had gone into the game 10 points behind PSG, meaning even a draw would not be good enough to postpone PSG's inevitable title triumph for just another day.
However, Les Rouges et Blancs looked worryingly devoid of ideas during a dour first half, with Berbatov even pleading with his team-mates for some movement ahead of him at one point.
As it was, the best Monaco could muster was a Ricardo Carvalho set-piece header that never looked like threatening the Ajaccio goal.
Berbatov, though, took the game by the scruff of the neck in the second half.
The Bulgarian opened the scoring in the 53rd minute with a flicked header from a Jao Moutinho cross from the left flank.
The former Manchester United forward struck again just over 20 minutes later, this time rolling the ball past Ajaccio goalkeeper Guillermo Ochoa with typical nonchalance, after being put in on goal by James Rodriguez's perfectly-weighted pass.
Ajaccio halved their deficit less than a minute later, with Tallo firing Dennis Oliech's low cross high into the roof of the Monaco net, but there was to be no denying Monaco.
With just two minutes remaining, Berbatov laid the ball off for the onrushing Kondogbia, who beat Ochoa with a wonderfully controlled drive from some 25 yards out.
Monaco then made sure of all three points when Ocampos volleyed home left-footed at the back post moments later.