Background: Mood Swings (MS) is a condition widely discussed as a prominent feature with psychiatric patients. However, there is a lack of research related MS. Methods: This school-based, cross-sectional study aimed to investigate the prevalence and distribution pattern of mood swings on personal and contextual determinants in Thai adolescent. The participants were 2,598 students in high school and vocational school in Bangkok and central region of Thailand. Results : the prevalence of mood swings was 26.4%. It was most frequent among the vocational students in Bangkok, there was 37.1%. The distribution of mood swings could be found in adolescents who had risk behaviors and who resided in hazardous situation. The probabilities of MS by characteristic in those 15 – 24 years old were: bullying involvement 36.9% (n=1293), problematic social media use 55.9%(n=127), high expressed emotion in family 36.6% (n=1256), and studying in vocational program 29.5%(n=1,216) and school located in Bangkok 32.4%(n=561). Also, substance use was a risk to MS as with cannabis 41.8%(n=55) and heroin users 48.0%(n=25). Hierarchical logistic regression analysis showed that being female, the family history of mental problems, bullying involvement, problematic social media use, high expressed emotion in family, and the interaction between vocational programs and metropolitan/urban residence were impacted adolescent mood swings (p < .05). Conclusions: our findings indicate that the pattern of mood swings was associated with significant bullying involvement, social media use, family circumstance and school characteristics. The public needs greater awareness of mood swings patterns and the positive implications of MS screening. Moreover, early preventive interventions which may stem later mental illness are needed. Keywords : Mood swings, Adolescent, Prevalence, Distribution