Objectives: To determine the population-based prevalence of albuminuria in Australian children and validate any negative correlation with body mass index (BMI). Methods: Data from the Australian Health Survey 2011–2013 were used. This is a large-scale survey of the health of the Australian population, conducted by the Australian Bureau of Statistics, and uses a stratified, multistage area design with replicate weights attached to observations to allow for the derivation of accurate population estimates. We considered children aged 5–18 years, and defined albuminuria as an albumin-to-creatinine ratio (ACR) >30 mg/g (3.4 mg/mmol). Results: A total of 975 children provided urine samples for determination of ACR. The prevalence of albuminuria was 10.2% for males (95% confidence interval [CI] 6.1–14.2) and 15.5% for females (95% CI 10.7–20.3). After adjusting for age and gender, the odds ratio for albuminuria associated with being overweight or obese was 0.34 (95% CI 0.15–0.75). This relationship also held for waist-to-height ratio, where the adjusted odds ratio for each 0.1 increase was 0.46 (95% CI 0.26–0.82). Conclusions: Albuminuria, using a measurement suitable for population-based and clinical screening, occurs in 12.8% of school-aged Australian children, and is less common in overweight and obese children.