Well-organized management of a supply chain involves the control of inventory levels and fast response to the changing customer demands. Enterprises cannot cope with this problem which contributes to the growing stock levels and therefore increases costs. The main goal of the article is to present a simulation approach to the problem of inventory management in a supply chain. The work shows the use of computer simulation techniques in order to emulate a supply chain system and its stochastic behaviour. The procedure for the usage of simulation modelling was described in a case study containing an analysis of an online store. The simulation results are presented using statistical parameters, which means that managers can get not only information concerning the expected value of the parameter looking decision-making, but also statistics to the characteristics of the risk associated with the decision associated with possible uncertainty.