This study aims to investigate to what extent the variables of social support, internalizing behaviours and academic achievement predict adolescent risk behaviours. The sample population consists of 491 high school students in grades 9, 10, 11 and 12 who were randomly selected out of 6 different high schools in Ankara. Our data collection instruments include the Risk Behaviours Scale (Gengtamrim & Ergene, 2014), the Youth Self Report for 11-18 Year Old Adolescents (Erol & Simsek, 1998), the Perceived Social Support Scale (Yildirim, 2004), and a personal information form. We employed a structural equation model (SEM) to determine the strength of independent variables to predict the risk behaviours in question. Results indicated the significance of the model developed to predict adolescent risk behaviours. Accordingly, adolescent risk behaviours were significantly predicted by social support, rather than academic achievement and internalizing behaviours.