Bullwhip effect is one of the key managerial issues in supply chain management and indicates the increase in demand of the last customer in the supply chain by moving throughout the chain. Qazvin National Oil Products Distribution Company faces many problems, such as the lack of visibility of final demand, lack of effective support, delays in product delivery, high cost of ordering, random ordering, inappropriate pricing, and etc. The main purpose of this paper is to identify determinants of bullwhip effect in the supply chain of this company using Fuzzy Delphi group decision making techniques. According to the results, there are 9 effective factors classified into 4 groups: demand factors, orders, price fluctuations and informational factors. Finally, solutions corresponding to each factor are presented