Childhood overweight/obesity has been associated with environmental, parenting and socioeconomic status (SES) factors. This paper assesses the influence of the amount of green space, accessibility to a garden and neighbourhood condition on being overweight/obese. It investigates whether parental behaviours moderate or mediate this influence and evaluates the interaction of SES with environmental context. 6467 children from the UK Millennium Cohort Study living in England were analysed. We estimated logistic regressions to examine the initial association between environment and overweight. Subsequently, parenting determinants comprising: food consumption, physical activity, rules and regularity were evaluated as moderators or mediators. Lastly SES related variables were tested as moderators or mediators of the associations. Statistically significant associations were found between low levels of green space, no access to a garden, run down area and childhood overweight/obesity odds ratio (OR) 95% confidence interval (CI) respectively: 1.14 (1.02-1.27), 1.35 (1.16-1.58), 1.22 (1.05-1.42). None of the parental constructs mediated or moderated the relationships between environment and childhood overweight/obesity. Including SES, parental education moderated the effect of environmental context. Specifically, among lower educated households lack of garden access and less green space was associated with overweight/obesity; and among higher educated households poor neighbourhood condition influenced the probability of overweight/obesity respectively: 1.38 (1.12-1.70) OR 1.38, 95% CI (1.21-1.70). This study suggests that limits on access to outdoor space are associated with future childhood overweight/obesity although the ways in which this occurs are moderated by parental education level.