Purpose: This study aims to investigate the socioeconomic disparities in health risk behavior clusterings among Korean adolescents and to assess the mediating role of stress on this association. Methods: We analyzed the 2015 Korean Youth Risk Behavior Survey, a nationally representative sample of Korean middle and high school students aged 12-18 years (N=68,043). The co-occurrence of multiple health risk behaviors (i.e., cigarette smoking, drinking, and unprotected sex) was used to operationalize health risk behavior clusterings that ranged from 0 to 3. Ordinal and multinomial logistic regressions were conducted to examine socioeconomic disparities in health risk behavior clusterings and mediating effect of perceived stress between socioeconomic status (SES) and health risk behaviors. Results: When SES was grouped into five groups, adolescents in the lowest SES [adjusted odds ratio (AOR) = 2.15, 95% confidence interval (CI) = 1.90-2.44] and highest SES (AOR = 1.29, 95% CI = 1.18-1.40) showed a higher likelihood of risk behavior clusterings than any other SES groups. Stress partially mediated the relationship between SES and co-occurrence of multiple health risk behaviors while accounting for their demographic characteristics. Adolescents in the lowest and highest SES reported higher stress than other SES groups, which, in turn, was associated with the co-occurrence of multiple health risk behaviors. Conclusions: The results suggest that perceived stress level partly explains why affluent as well as low-SES adolescents engage in multiple risk behaviors. The findings also discourage use of a linear approach in socioeconomic disparities investigation in relation to adolescent health behaviors.