Bothrops moojeni has a wide distribution in Brazil and represents a serious medical concern at some localities. Previous works reported that the manifestations of snakebites caused by B. moojeni juveniles were mainly related to coagulation, while those caused by adults had more prominent local damage. In this work, we aimed to analyze the venoms of B. moojeni at different life stages to better understand how the venom shifts along the ontogeny. Snakes were grouped by age and sex, and venom pools were formed accordingly. Compositional analyses by one-dimensional electrophoresis (1-DE), chromatography and mass spectrometry revealed that ontogenetic changes may be mostly related to phospholipase A2 (PLA2) and metalloproteases. Regarding the functional aspect of the venoms, in vitro assays of proteolytic, L-amino acid oxidase, PLA2 and coagulant activities were assayed, but only the first and the last showed age-related changes, with the venom of younger snakes displaying lower proteolytic and higher coagulant activities up to 1 year-old; from 2 years-old onward, the venoms presented the opposite relation. The venoms of 3 years-old snakes were exceptions to the compositional and functional pattern of adults. Sex-related differences were observed at specific groups and not related to age. In vivo experiments (median lethal dose and hemorrhagic activity) were statistically similar between neonates and adults, but observation of the time each venom took to kill the mice revealed that the adult one seemed to act faster than the venoms of the neonates. All venoms were mostly recognized by the antibothropic serum and displayed similar profiles to 1-DE in western blotting. In conclusion, the venoms showed ontogenetic shift in composition and activities. Furthermore, this change occurred from 1 to 2 years-old, and interestingly the 3 years-old pools had particular characteristics, which highlight the importance of extending the studies to better understand venom variability.