The available information on the contribution of family circumstance to adolescent dietary behaviours is inconsistent. Indicators of family circumstance may impact adolescent behaviours by influencing their daily home environment. This study examined cross-sectional and longitudinal relationships between indicators of family circumstance and (i) breakfast skipping and (ii) consumption of snack food, fast food, fruits and vegetables among adolescents. Dietary behaviour was assessed using a web-based survey completed by 1884 adolescents from years 7 and 9 of secondary schools in Victoria, Australia, at baseline and 2 years later. Five indicators of family circumstance (parental marital status, maternal education, maternal employment status, number of brothers and number of sisters) were assessed with a questionnaire completed by parents at baseline only. Logistic regression was used to examine cross-sectional associations between indicators of family circumstance and dietary behaviours. Multinomial logistic regression was used to examine associations between indicators of family circumstance and 2-year change in dietary behaviours. Individual indicators of family circumstance were differentially associated with adolescent dietary behaviours. Cross-sectional and longitudinal associations differed for adolescent boys and girls highlighting the importance of assessing specific dietary behaviours and food types individually by gender. This study highlights the complexity of the relationships between family circumstance and adolescent dietary behaviours. Future research needs to assess the efficacy of strategies promoting maternal nutritional knowledge on the dietary behaviours of adolescents.