A child’s home food environment (HFE) supports or inhibits healthy eating, but its influence on childhood obesity is unclear due to poor understanding of underlying dimensions and mechanisms. This study aimed to investigate the relationship between the HFE and childhood obesity as mediated by child diet. Baseline data collected by questionnaire from parents of children (9–11 years old) participating in the Obesity Prevention and Lifestyle(OPAL) Program were used (n=3323). Exploratory factor analysis using polychoric correlation explored 21 underlying components of the HFE. These components were used to define the overall HFE and linked to child diet (defined as meeting guidelines for fruit, vegetable and non-core food intake, based on parent report of child intake of defined food groups the previous day) and measured child BMI in structural equation modelling, adjusting for confounders. Five components incorporating 10 items were retained to describe HFE. After adjusting for age, gender, socioeconomic status and physical activity, all associations in the model were significant(p < 0.05) and explained 9.3% and 4.5% of variance in child diet and BMI respectively. Our model was a good fit and showed that a more positive HFE was directly associated, and indirectly associated through child diet, with a lower BMI in children. Parents are important facilitators of primary schoolchildren’s healthy eating at home. The robust statistical methodology used provides support for a model of the direct and indirect dynamics between the HFE and childhood obesity. The model can be tested in future longitudinal and intervention studies to identify the most effective HFE component that should be targeted in childhood obesity prevention efforts.