BACKGROUND Adolescents represent approximately one-fifth of the total population of Thailand. Few comprehensive surveys of adolescents living in Bangkok slums are available in the literature. To appropriately consider adolescents' development in urban planning strategies calls for the study of the relationship between depression and quality of life (QoL) of adolescents in slums. This study aimed to assess the level of depression and to describe the relationship between depression and QoL for the adolescents in a slum community of Bangkok. METHODS This is a descriptive study. Data from eight hundred and seventy-one adolescents in a Bangkok slum community were randomly collected by a survey that utilized a socio-demographic questionnaire, the Center for Epidemiologic Studies Depression (CES-D) scale for depression level, and the World Health Organization Quality of Life Brief (WHOQoL-BREF) assessment, Thai version, for quality of life. RESULTS Thirty-four point nine percent of all respondents exhibited depressive symptoms: 27.6% of males and 40.4% of females. Twenty-six percent of adolescents indicated that they had a 'poor' quality of life. A Chi-squared test yielded a statistically significant difference in the level of depression according to the level of QoL when both genders were considered together (p < 0.001). Multiple regression analysis shown the association between depression and three factors: quality of life (p < 0.001), position in the family (p = 0.04) and the adolescent's place of origin (p = 0.02). CONCLUSIONS These findings suggest channels to help adolescents with depression in Bangkok slum communities. Specifically, based on the findings, interventions for adolescent depression may be more effective if gender, age group and family participation in the adolescent's development are considered in the planning and implementation of health intervention programs.