Substance abuse affects the mental health of tribal adolescents. A community based cross sectional study was conducted among 87 tribal adolescents in South Kerala to assess the prevalence of substance abuse and explored the association between mental health and substance abuse. Data was collected using predesigned and pretested questionnaire by house to house survey method using one to one interview technique. The prevalence of substance abuse was 52.9%. 65.2% males in their late adolescence were found abusers. 16.1% and 83.9%   of tribal adolescents had good and poor mental health respectively. Among tribal adolescents with good and poor mental health status it was found that 7.1% and 52.9% respectively were substance abusers and this difference observed was found to be statistically highly significant (p<0.001). To conclude, there is high prevalence of substance abuse among tribal adolescents associated with poor mental health status. Awareness generation on prevention of substance abuse using all sources of media and counseling on mental health are felt needs among tribal adolescents.