The overall aim of this study was to examine obesogenic factors in children from single and dual parent families. Data from the Longitudinal Study of Australian Children (LSAC) (8,717 children) were analyzed to examine the differences in children's activity levels, dietary intake and BMI according to parental status and determine the likelihood of childhood overweight and obesity in a single-parent household. There were higher rates of overweight and obesity in girls aged four to nine whose parents were single (OR 1:60). Children in single-parent households watched more television, ate more food high in fat and sugar and less fresh fruit and vegetables than children from dual-parent households. The findings suggested that an additive effect of dietary and activity variables may contribute to the higher rates of overweight and obesity in Australian children, and that girls from single-parent households may be particularly at risk.