The current study examined the stability/change trajectories of sense of agency across high school, analyzing whether these trajectories are influenced by attachment to parents over time, as well as adolescent’s sex, psychosocial risk in baseline, and pandemic stress. The sample includes 467 Portuguese adolescents (59.3% were females; Mage = 15.58 years, SD = .80), who were evaluated three times across 18 months. This work yielded three major findings. First, we found that adolescents’ sense of agency significantly increased over time, with significant inter-subject variance at the initial levels, but not at the growth rate. Second, we observed a stable effect of attachment to parents on sense of agency across late adolescence. Further, we found differential effects of attachment to father versus mother on agency beliefs. Third, we verified that boys reported a greater growth of sense of agency than girls; that adolescents who experienced higher levels of multiple risks in T1 showed lower initial levels of sense of agency; and that adolescents who reported higher levels of pandemic-related stress reported less growth of sense of agency. These findings emphasize the role of individual and family characteristics, as well as the role of the wider social context in shaping the development of sense of agency during adolescence. Moreover, the findings underline the need to consider differential influences in the relationship with fathers versus mothers to gain a better understanding of changes in agency beliefs.