This study explored how Psychosocial Predictors of Sexual Decision-Making among In-School Adolescents in Bayelsa State, Nigeria. Adolescents is a pivotal developmental period marked by rapid physical, emotional, and social changes, during which external social contexts and internal psychological resources strongly shape sexual decision-making. A correlational survey design was adopted to examine these relationships without experimental manipulation. The population comprised Junior Secondary School II and III students aged 13–19 years attending public and private secondary schools in the study area. Using Cochran’s sampling formula, 450 adolescents were selected through stratified random sampling to ensure proportional representation across gender, school type, and socio-economic status. Data were analysed using Pearson’s product– moment correlation and multiple regression techniques. The results showed that sexual risktaking behaviours had a significant negative relationship with parental practices (r = –0.428, p < 0.01) and self-esteem (r = –0.366, p < 0.01), indicating that stronger parental monitoring, guidance, and emotional support, as well as higher self-worth, were associated with lower engagement in risky sexual activities. Conversely, peer influence demonstrated a significant positive relationship with sexual risk-taking behaviours (r = 0.472, p < 0.01), suggesting increased vulnerability among adolescents who are highly susceptible to peer pressure. The multiple regression analysis further revealed that parental practices, peer influence, and self-esteem jointly explained 54.4% of the variance in adolescents’ sexual risk-taking behaviours (R² = 0.544, Adjusted R² = 0.541, F = 217.45, p < 0.01). In terms of relative contribution, parental practices (β = – 0.388, p < 0.01) and self-esteem (β = –0.279, p < 0.01) emerged as significant negative predictors, while peer influence (β = 0.435, p < 0.01) was a significant positive predictor. The study underscores the importance of addressing family dynamics, peer environments, and adolescents’ psychological resources in efforts to curb sexual risk-taking behaviours. It recommends the integration of parent-focused guidance programmes, peer-based educational initiatives, and self-esteem enhancement strategies within school and community counselling interventions to promote healthier sexual decision-making among adolescents.