Insect antimicrobial peptides (AMPs) have been characterized more than 150 peptides since identification of cecropin in the hemolymph of pupae from Hyalophora cecropia in 1980. Therefore, it is considered that insects are good species of AMPs selection. Insect AMPs are small (below 10 kDa), cationic, and amphipathic with variable length, sequence, and structure. They perform a critical role on humoral immunity in the insect innate immune system against invading pathogens such as bacteria, fungi, parasites, and viruses. Most of insect AMPs are induced rapidly in the fat bodies and other specific tissues of insects after septic injury or immune challenge. Then the AMPs subsequently released into the hemolymph to act against microorganisms. These peptides have a broad antimicrobial spectrum against various microorganisms including anticancer activities. Insect AMPs can be divided into four families based on their structures and sequences. That is α-helical peptides, cysteine-rich peptides, proline-rich peptides, and glycine-rich peptides/proteins. For instance, cecropins, insect defensins, proline-rich peptides, and attacins are common insect AMPs, but gloverins and moricins have been identified only in lepidopteran species. In this presentation, we focus on AMPs from insects and discuss current knowledge and recent progresses with potential application of insect AMPs.