The striker was afforded a rare start in the Parc des Princes, and repaid his manager's faith by scoring both goals in a victory that saw Les Parisiens move to second in Ligue 1.
"Kevin Gameiro worked very well and had a fantastic match," Ligue1.com quoted Ancelotti as saying. "It shows that he hasn't lost any confidence and he deserved to score his goals tonight.
"We were, however, not brilliant in the second half. That wasn't good. It's true Sochaux came at us and attacked us but we need to play with more rhythm. Perhaps some of the players were already thinking about the next games."
Gameiro scored 11 goals in 27 appearances last season.