The former Manchester United star played for 86 minutes during the 2-0 victory over Olympique Marseille in the French cup.
"He made a very good game. He showed that he can play. I think that he did not look like he was 37 tonight," Ancelotti told reporters.
"He made good passes as usual, he was well positioned on the pitch alongside Blaise Matuidi. He was very solid.
"He can bring a lot of things, his passing skills, his experience, his [aggression]."
Beckham himself said that he enjoyed his first start, but admitted he is not yet ready to play for a full 90 minutes.
"It's always nice to start. I really enjoy playing in this team, with special players like these ones," he said.
"If I am tired? Not really. I feel good though I certainly am not ready to play 90 minutes."
Beckham made his PSG debut with a substitute appearance against Marseille in the league last weekend.