Resource constrained project scheduling problem (RCPSP) is one of the most important problems in industrial engineering and production management. Owing to environmental concerns, companies are paying more attention to the remanufacturing of end-of-life products. In this thesis, a mathematical model is developed considering remanufacturing activities in resource constrained project scheduling problem. The mathematical model considers recycle rate in multiple operation modes and several components of cost, including bonus, penalty, and others. A set of project network instance are generated using RanGen1 for evaluation. To solve the model, a three-stage heuristic method is developed in CPLEX 12.8 environment. Result shows that proposed method can reach a close-to-optimal solution within acceptable time limit.