The 37-year-old is yet to feature for the Ligue 1 leaders following his January deadline day move, but Ancelotti has confirmed that the former England captain is ready to pull on the PSG shirt for the first time.
"Beckham is available," he told BeIn Sport. "He has worked well. He wants to play. He's in good physical condition, that's what's important. If he starts, it will be in the midfield. Maybe he will start.
"Starting him would not be a risk because he's a player in good shape physically. If he starts, he can play 60 or 70 minutes. If he's on the bench, he will play for maybe 30 or 40 minutes.
"All of the tests are positive. He's a player in top shape. He's always focused. He's always professional. I won't be giving away my starting XI here."
The Italian added his belief that Beckham will work well with striker Zlatan Ibrahimovic, who he has backed to perform following a disappointing showing in the defeat to Sochaux.
"Ibrahimovic and Beckham have the same objective," he continued. "They fit well together and have a good relationship. They both want to win the title. They are stars, but they are also important players. I'm happy to have them, put simply.
"Zlatan was having difficulty against Sochaux but, after this week of work, we will see a quicker, more aggressive Ibra. I'm sure that he will have a great match tomorrow."
Victory for PSG on Sunday would open up an eight point gap on Marseille, and Ancelotti admits that such an advantage could prove crucial in deciding the destiny of the title.
"I have a lot of respect for Marseille. They're a team who win a lot away because they have experience," the former Chelsea coach went on.
"Marseille are a strong team physically with good attacking players like the Ayew brothers [Andre and Jordan] or [Mathieu] Valbuena. It will be an attacking, heated match - that's what a Classique is like. I hope that it will be a good match to watch, too.
"It's a very important match. To have Marseille eight points behind us would be very good for us. We will play to win tomorrow; we can win with a good defense or a good attack."