Matija Nastasic and Ralf Fahrmann have committed their futures to Schalke by signing new contracts that run until 2022.
Centre-back Nastasic and goalkeeper Farhmann were key players as Domenico Tedesco's side finished second in the Bundesliga behind champions Bayern Munich.
Captain Fahrmann was one of two ever-present players as Schalke qualified for the Champions League, with Naldo the other to start all 34 league games.
Nastasic's contract renewal will come as a welcome boost after he missed out on Serbia's final 23-man squad for the World Cup, having failed to prove his fitness.
The former Manchester City defender missed the end of the Bundesliga season with a knee ligament injury and was unable to recover in time to go to Russia.