Arthropod-borne viruses (arboviruses) are a significant cause of human diseases worldwide. Interactions between these viruses and the innate immune system play a major role in determining the outcome of disease. The complement system is particularly important in this process as activation of complement can contribute to both host defense as well as injury to host tissues. This review focuses on the increasing evidence that the complement system plays key roles in both protective and pathologic outcomes of arbovirus infection.