The 37-year-old came off the bench to play a part in his new club's second goal as PSG picked up a 2-0 win over their title rivals.
The capital club are now three points clear of Lyon in Ligue 1, and Ancelotti was delighted by the former England captain's impact.
"He came on because Marco Verratti was tired and we needed fresh players on the pitch," Ancelotti told Sky Sports News.
"He showed quality with his passes, his experience. He showed good qualities, even if it was difficult to judge in only 20 minutes."
Asked if Beckham could start against Marseille at the Parc des Princes on Wednesday in the in the Coupe de France, Ancelotti said: "Perhaps. Verratti is suspended, so maybe he will play."
Beckham joined PSG on transfer deadline day last month.