The aim of this study is to propose a methodology to estimate the age of individuals of capybaras (Hydrochoerus hydrochaeris) using some morphometric measurements of the skull and femur. A sample of 250 individuals from different age categories was analyzed. These categories were estimated based on the ossification degree of the cranial sutures. Out of 28 morphocranial measurements taken, nine of them allow us to adequately determine the degree of bone maturation and the relative age: pre maxillonasal maximum width (MNW), pre maxillonasal minimum width (MNMW), parietal width (PW), intermaxillary width (IMW), maximum width of the 3rd molar (MW), minimum width of the 3rd molar (MMW), 3rd molar length (M3), molar length (ML), and molar 1 and 2 length (M12). In case of the femur, the measurements did not show differences among age categories, thus, we discarded these morphometric magnitudes as possible age indicators. This work proposes new measures to estimate and to analyze the relative age structure of the capybara population, providing a useful tool in the management and conservation of this species, and to evaluate paleontological and archaeological assemblages.