Last year's Ballon d'Or winner Benzema did not travel to Morocco earlier this week for the tournament, having sustained a hamstring injury.
However, Ancelotti confirmed after Madrid beat Al Ahly 4-1 in their semi-final that the 35 year-old will travel out to train with his team-mates on Saturday (AEDT).
Benzema will be joined by Eder Militao, though Ancelotti – who confirmed Marco Asensio and Dani Carvajal were kept on the bench against Al Ahly due to issues with their fitness – harbours more doubts over the defender's possible contention for Sunday's (AEDT) clash with Al-Hilal.
"They are not fully recovered," Ancelotti said. "Karim is doing pretty well and there are more doubts about Militao.
"They will train on Friday and then we will see.
"Carvajal had a fever and Asensio a little overload. I think he will be ready for Saturday."
Madrid is going for a record-extending fifth Club World Cup title, with its first success coming under Ancelotti in Morocco in December 2014.
"Preparing it well, giving clear instructions to the players and introducing a good strategy," Ancelotti replied when asked how he managed preparations for the mini-tournament.
"And then, it's the confidence that we have players who handle this type of pressure very well."
Saudi Arabian side Al-Hilal stunned Copa Libertadores champion Flamengo 3-2, and Ancelotti acknowledged he was shocked by that result.
"I was surprised. At an individual level [Flamengo] had an advantage, but they are in pre-season and their physical level is not top, like the rest of the teams. They paid for it."