The experienced midfield duo have not always been starters in recent weeks, with Los Blancos head coach Carlo Ancelotti rotating the pair out of the side.
However, Modric and Kroos are in the XI against Al Ahly, with Aurelien Tchouameni also featuring in midfield for the reigning Spanish and European champions.
Thibaut Courtois has not made the trip to Morocco due to a groin problem, which has opened the door for Andriy Lunin to again feature between the sticks.
Dani Carvajal has returned to fitness to ease Real Madrid's full-back problems, but the Spaniard is only on the bench, with Nacho skipping the side from right-back.
Fit-again David Alaba is joined in the middle of the defence by Antonio Rudiger, with Eder Militao also not making the trip for the competition due to a recent injury.
Ferland Mendy is also absent, with Eduardo Camavinga keeping hold of the left-back position for this match.
Karim Benzema is missing from the squad due to a hamstring issue, which has opened the door for Rodrygo to feature through the middle for Ancelotti's side.
Federico Valverde and Vinicius Junior are also present in the final third of the field, while there is a spot on the bench for Marco Asensio despite concerns that he could miss out through injury.
Dani Ceballos and Mariano Diaz are also among the substitutes, but it is a youthful bench, with Mario Martin and Sergio Arribas among those in reserve.
Real Madrid are the most successful side in the history of the Club World Cup, having lifted the trophy on four occasions, with their last triumph in the competition coming in 2018.
Should Los Blancos advance, they would take on Al-Hilal in Saturday's final, with the Saudi Arabian outfit beating Flamengo 3-2 in the first semi-final on Tuesday.
Real Madrid XI vs. Al Ahly: Lunin; Nacho, Alaba, Rudiger, Camavinga; Kroos, Tchouameni, Modric; Valverde, Rodrygo, Vinicius