Objective: To examine demographic and behavioural correlates of frequent consumption of fast food among Australian secondary school students and explore the associations between fast food consumption and social/environmental factors.Design: Cross-sectional survey using a web-based self-report questionnaire.Setting: Secondary schools across all Australian states and territories.Participants: Students aged 12-17 years participating in the 2012-2013 National Secondary Students' Diet and Activity survey (n 8392).Results: Overall, 38 % of students surveyed reported consuming fast food at least weekly. Being male, residing in lower socio-economic areas and metropolitan locations, having more weekly spending money and working at a fast food outlet were all independently associated with consuming fast food once a week or more, as were several unhealthy eating (low vegetable intake and high sugary drink and snack food intake) and leisure (low physical activity and higher commercial television viewing) behaviours and short sleep duration. Frequent fast food consumption and measured weight status were unrelated. Students who agreed they go to fast food outlets with their family and friends were more likely to report consuming fast food at least weekly, as were those who usually 'upsize' their fast food meals and believe fast food is good value for money.Conclusions: These results suggest that frequent fast food consumption clusters with other unhealthy behaviours. Policy and educational interventions that reach identified at-risk groups are needed to reduce adolescent fast food consumption at the population level. Policies placing restrictions on the portion sizes of fast food may also help adolescents limit their intake.