This study aimed to investigate the prevalence and determinants of adolescent heterosexual behaviors among senior secondary school students in Rivers State, Nigeria. Employing a descriptive cross-sectional research design, the study targeted a sample size of 1,200 students drawn from a total population of 185,225. The reliability of the research instruments was confirmed using the split-half method, yielding a coefficient of 0.77, while face and content validity were ensured. Descriptive statistics, including frequency, percentages, mean, and standard deviation, were used to address the research questions, and the chi-square test was applied to examine the relationships between variables. The findings revealed that 57.0% of the surveyed adolescents exhibited various heterosexual behaviors. Among these, 63.3% reported kissing the opposite sex, 62.1% engaged in sexual intercourse, 76.0% practiced oral sex, 67.7% engaged in anal sex, and 51.9% reported masturbation. Furthermore, a significant relationship was found between age and the prevalence of these behaviors (X2 = 14.200, df = 7, p < .05). Based on these results, the study recommends that public health officials and policymakers develop frameworks to regulate online content and information accessed by children and adolescents. Additionally, parents should take an active role in monitoring their children’s health and social well-being to prevent risky sexual behaviors and their potential reproductive health consequences