Food loss and waste are of global concern. In developing countries like Mozambique, it seems to be a major issue at the upstream end of supply chains, which is also regarded as postharvest losses (PHL). In this study, PHL is analysed in the context of maize in Mozambique, which is the most important crop in that country. The analysis focuses on empirically testing a simulation modelling approach for determining the short and mid-run economic impacts of PHL. A system dynamics modelis applied. This model acknowledges climate, management, and domestic and regional marketing related factors as major drivers of PHL. A novel result from this study suggests climate related factors as the cause of a systematic amount of PHL at about 70,000 tons per year.However, marketing forces also play an important role to explain the overall PHL, particularly in periods domestic production increases sharply. The impact of potential interventions in the value chain is also tested.