Substitution occurs when a customer cannot purchase the originally requested product due to stockout and might buy a substitutable or similar product. Substitution also occurs when a customer might purchase a substitutable product if the price of the originally requested product changes, which is referred to as price-drive substitution. In this study, we consider a stochastic optimization model for deciding the optimal prices and ordering quantities in the presence of price-driven substitution. We also compare the existing deterministic price-driven substitution model with the stochastic price-driven substitution model of this research. The objective of this study is to investigate the impact of price-driven substitution on the optimal solutions and the expected profits through theoretical analysis and numerical experiments.