Understanding infectious diseases in wildlife is important in conservation as well as public health, because most infectious diseases are zoonotic. The role of many zoonoses in the chain of infection of some infectious agents is still poorly understood. Adenovirus infections have been described in fish, amphibians, reptiles, birds and mammals. Non-human primates can be reservoirs of various infectious diseases and may be important for public health when close to humans in rural and urban areas. We investigated the presence of Adenovirus in faecal samples of 50 road-killed Geoffroy’s tufted-ear marmosets from suburban areas in the state of Espírito Santo, southeastern Brazil. Two samples (4%) were positive. Phylogenetic analysis show that the viruses are related to the genus Atadenovirus and Mastadenovirus. Their non-specificity suggests that these viruses are food-borne. Adenoviruses are very common in human infections, and may affect other vertebrate species. They can cause eye, gastrointestinal and respiratory infections, some of which can be fatal. This is the first record of Adenovirus in a wild population of Callithrix geoffroyi. The investigation of infectious diseases in free-living animals is important to determine the susceptible species to each infectious agent, and to establish the possible transmission of diseases between wild species and their zoonotic potential. Nevertheless, these studies are still uncommon due to the difficulty in obtaining samples. The use of road-killed animals in scientific studies provides access to otherwise unavailable biological material and contributes to investigation and monitoring of viral infections in the wild.