Insect pests in postharvest systems in the most of countries, which can include bulk grains in storage, and also the milling, processing, storage, and retail industries, account for millions of dollars of losses each year in direct and indirect costs. Insect pests in harvested fresh commodities can lead to huge economic losses due to rejections of shipments, restrictions on shipments, reduction of market quality, and reduction of market price. Reduction in pest risk to exported fresh commodities as a phytosanitary measure involves some key postharvest steps. Some of the major insect pests are common to different postharvest systems while others are unique to one particular system. In this article, the major postharvest insect pests and their impacts will be discussed for grains and processed grain products, tree nuts, and fresh fruit crops.