Consistent behavioral differences among individuals, that is, personality, are described in numerous species. Nevertheless, the development of behavioral consistency over ontogeny remains unclear, including whether the personality of individuals is consistent throughout life, and if adult personality can be predicted already at young age. We investigated the ontogeny of personality in the red junglefowl (Gallus gallus) by scoring personality of hatchlings at 5 time points through adulthood, including before and after the major developmental stages of becoming independent and sexual mature. We use the conceptual framework laid out by Stamps and Groothuis (2010a) to holistically investigate the observed changes in behavioral response over ontogeny. We demonstrate that mean values of behavioral responses changed across ontogeny and stabilized after independence. Rank-order consistencies of behavioral responses were overall low across independence and sexual maturation. Only in 1 case could low rank-order consistencies potentially be explained by different phenotypes displaying different amounts of change in behavior; more explorative individuals decreased in exploration after independence, while less explorative individuals remained so. Correlations among behavior varied across ontogeny and weakened after sexual maturation. Our results demonstrate that both absolute values and consistency of behavioral traits may change across ontogeny and that individual developmental trajectories and adult personality only to some extent can be predicted early in life. These results have implications for future studies on personality, highlighting that the life stage at which individuals are scored affects the observed consistency of behavioral responses.