Games went by way of serve in the early stages of the opening set, and it took the 10th game for Tsonga to find the breakthrough and win the set.
Tsonga suffered an early blow in the second set by losing his first service game, but he later responded by breaking back on the clay court.
It took another break from Tsonga to ensure a two-set lead in Paris, leaving his opponent with a mountain to climb in the third.
Janowicz started off strongly by earning a break of serve at the first time of asking, but immediately Tsonga broke back to keep dominating proceedings.
Another break gave the Frenchman a comfortable lead as he went on to win the contest.