Food insecurity is defined as the inability of people in socially vulnerable situations to obtain food in sufficient quantity and quality to meet their needs for a healthy life. On the other hand, food banks are institutions that can help alleviate, in the short term, the symptoms of food insecurity, which can be considered a long-term crisis. The supply chain of a food bank is established in a complex environment, involving a rapidly growing demand (increased poverty and food insecurity, especially in developing countries), a low adherence of food donors, associated with several factors limiting factors such as physical resources, human resources, infrastructure, among others. This article aims to identify the processes that form the humanitarian assistance chain of a food bank and the connection between them. To this end, this article demonstrates the step-by-step process for constructing a causal loop diagram that represents these processes and the associated complexities. The results provide an understanding of the variables, their relationships and complexities in the search for an increase in the number of beneficiaries served by the food bank.