We evaluated the epidemiological evidence on the built environment and its link to childhood obesity, focusing on environmental factors such as traffic noise and air pollution, as well as physical factors potentially driving obesity-related behaviours, such as neighbourhood walkability and availability and accessibility of parks and playgrounds. Eligible studies were i) conducted on human children below the age of 18 years, ii) focused on body size measurements in childhood, iii) examined at least one built environment characteristic, iv) reported effect sizes and associated confidence intervals, and v) were published in English language. A z-Test, as alternative to the meta-analysis, was used to quantify associations due to heterogeneity in exposure and outcome definition. We found strong evidence for an association of traffic-related air pollution (nitrogen dioxide and nitrogen oxides exposure; p<0.001) and built environment characteristics supportive of walking (street intersection density; p<0.01 and access to parks; p<0.001) with childhood obesity. We identified a lack of studies which account for interactions between different built environment exposures or verify the role and mechanism of important effect modifiers such as age.