This study examined the relationship between behavioural addictions and mental well-being among secondary school students in the Uyo Education Zone, Akwa Ibom State, Nigeria. Specifically, the study focused on two behavioural addiction variables: compulsive social media use and compulsive gaming. A correlational research design was adopted, with a sample of 250 Senior Secondary School Two students selected using multi-stage sampling techniques from a population of 12,847 students. The Behavioural Addictions and Mental Well-being Questionnaire (BAMWQ) was used for data collection, with a reliability coefficient of 0.82 obtained through the Cronbach Alpha method. Data were analyzed using the Pearson Product Moment Correlation (PPMC) at a 0.05 significance level. Findings revealed a significant, high negative relationship between compulsive social media use and mental well-being (r = -.505, p < .05), and a significant, moderate negative relationship between compulsive gaming and mental well-being (r = -.358, p < .05). The study concluded that behavioural addictions, particularly those related to digital media use, pose significant threats to adolescent mental health. Implications for guidance and counselling practice are discussed, and recommendations include integrating psycho-educational modules into school curricula and promoting healthy digital habits among students.