Real Madrid lost Courtois to a groin injury ahead of the 1-0 loss to Mallorca in La Liga on Sunday afternoon, while Benzema is nursing a hamstring problem that he suffered against Valencia last week.
Neither issue is believed to be serious, but the pair will not feature in the Club World Cup in Morocco.
Carlo Ancelotti's side will take on Al Ahly in the semi-finals of the competition on Wednesday evening ahead of a possible final against Flamengo or Al-Hilal on Saturday night.
Eder Militao is also on the treatment table, as the Brazilian, like Benzema, was forced off against Valencia last week following a clash with Samuel Lino.
Eden Hazard is back on the sidelines, meanwhile, with the Belgian struggling with a knee problem.
Ferland Mendy and Lucas Vazquez are also out for Ancelotti's side, with the former currently nursing a thigh injury, while the latter is out with an ankle issue.
As a result, Real Madrid will be missing six players for the tournament, but David Alaba is included after returning from injury in the 1-0 defeat to Mallorca at the weekend.
The first-team absentees means that there are call-ups for Mario Martin, Sergio Arribas and Marvel, while Mariano Diaz could be given a chance to impress in the final third due to a lack of options.
Andriy Lunin will benefit from Courtois's absence to continue between the sticks, while Luka Modric and Toni Kroos could return to the middle of the park after not being guaranteed starts in recent matches.
Real Madrid will be back in La Liga action against Elche on February 15 before travelling to Osasuna ahead of the first leg of their Champions League last-16 clash with Liverpool on February 21.
Real Madrid squad for Club World Cup:
Lunin, Lopez, Canizares; Carvajal, Alaba, Vallejo, Nacho, Odriozola, Rudiger, Marvel; Kroos, Modric, Camavinga, Valverde, Tchouameni, Ceballos, Martin, Arribas; Asensio, Vinicius, Rodrygo, Mariano