Abstract: Nowadays, the importance of careful planning to achieve goals in project-based organizations (PBOs) has become clear with the complexity of economic conditions and competitive conditions governing the receipt and implementation of projects. One of the most important of these plans is project scheduling, which is an attractive research field for the use of optimization methods among researchers in operation research due to its importance. This study was conducted to investigate the problem of robust integrated project scheduling and material ordering in terms of resource constraints, uncertainty, and lag times. Simultaneous consideration of discount, non-renewability, perishability, uncertainty, and different project implementation scenarios brought the model closer to real-world conditions and, as a result, made the results more practical. So, a scenario-based model was designed with the objective function to minimize the total cost (including ordering, maintenance, purchasing, and penalties for delay minus the bonus for hastening the project delivery). Model robustification was then performed with a possibilistic approach. After providing the model, numerical problems in different dimensions were designed and solved by using GAMS software, and the results were discussed. Keywords: robust model, material ordering, scheduling, uncertainty, discount, perishability.