The Tsonga v Isner match was a close affair throughout, with only one break of serve in the course of the match.
Isner broke in the sixth game and held serve to clinch the first set, but the sixth-seeded Tsonga, the 2008 Bercy champion, upped his game in the second set, forcing his opponent to serve big to stave off three break points.
Isner lost his cool in the tiebreak, won 7-1 by Tsonga, who enjoyed the backing of the 14,500 crowd.
The local favourite went 40-0 up on Isner's serve at 4-4 in the decider, but it was his time to lose composure, and the semi-final went down to the wire after Tsonga saved three match points in the 12th game.
Tsonga opened a 3-0 lead and won the tiebreaker 7-3 with a forehand winner down the line after two hours, 58 minutes.
"At the beginning I was too tense, but then I just tried to enjoy myself and that's how I play my best tennis," Tsonga told reporters.
"I'll have to be able to go into the court, go forward against Roger," Tsonga said.
Isner said of his defeat: "In tennis - just in any sport - you come so close to winning, and then it gets taken away from you.
"I had three chances. I was one point away from being in the final. So it wasn't to be. He came up with the goods, and hats off to him."