In this study, we address interpersonal violence during the transition between the Middle and the Late Formative periods in the Central Andes, a critical period of political disintegration, hypothesized population pressure, and reorganization of the belief systems that is poorly known from a bioarchaeological viewpoint. Our objective is to understand the nature of the violence and associated factors in this context based on a detailed description of skeletal trauma in 67 well-preserved individuals (20 adolescents and adults and 47 subadults) recovered from Quebrada Chupacigarro cemetery (500–400 BC); this site is located in the middle valley of Supe on the Peruvian north-central coast. To detect patterns and potential causes, we registered the prevalence of traumatic injury according to age, sex, anatomic location, mechanisms (blunt, sharp, mixed, etc.), timing (antemortem or perimortem), and manner (inflicted or accidental). The results show a high prevalence of fractures in the whole population, but especially in adolescents and adults. Eighty percent of the adolescents and adults perished due to the intentional trauma and show patterns that suggest repetitive episodes of interpersonal violence. Perimortem injuries in the skull, face, and thorax are compatible with lethal interpersonal violence. The findings support a probable scenario of intercommunity violence in the middle valley of Supe around 500–400 BC.