Kylian Mbappe's 15th Ligue 1 goal of the season put Monaco on track after 19 minutes and Valere Germain wrapped up the silverware by tapping in with the last kick of the game.
PSG had been widely expected to maintain their era of dominance and Jardim hailed his team's achievement as the highlight of his coaching career.
"Winning a championship in a team that is not a favourite is a great trophy," Jardim told Canal+.
"This is the most important trophy of my life as a coach. We have worked a lot for 11 months.
"But the best thing comes with this title. Monaco are champions, this is worth four titles for Paris."
Winning the Ligue 1 title for the eighth time caps a stunning rise for Monaco, who were playing in France's second tier five seasons ago.
Vice-president Vadim Vasilyev insisted the club would hold on to star names including Mbappe, Bernardo Silva and Thomas Lemar.
"Monaco has been waiting 17 years for this title," Vasilyev told Canal+. "It is exceptional. Good work always pays off.
"We were in Ligue 2 four years ago. I did not imagine that we could get there in such a short time.
"We're going to keep the players."