Oligoryzomys longicaudatus is the main reservoir of Andes virus (AND), which causes hantavirus pulmonary syndrome in Patagonia. The factors associated with the presence of antibodies against AND in this species are unknown. This study used a logistic regression model to analyze which characteristics of O. longicaudatus, captured in northern Argentinean Patagonia, led to an increased probability of an animal having antibodies against AND and to relate these characteristics to possible mechanisms of transmission of the virus within the population. Sex, age, body mass, and wounds were important predictors regarding the presence of antibodies against AND within O. longicaudatus populations. The probability of a wounded male O. longicaudatus adult having AND antibodies increased in parallel with the body mass. The probability of having antibodies was more than 80% in individuals with body masses above 44 gram. However, the possible transmission mechanism of AND within O. longicaudatus population is still uncertain and further studies involving a larger number of individuals and prolonged monitoring including the process of seroconversion are needed.