We estimated the relationship between religion and body mass index (BMI) for a general and representative sample of the Australia population. Data from the Household Income Labour Dynamics survey were analysed for 9,408 adults aged 18 and older. OLS regression analyses revealed that religious denomination was significantly related to higher BMI, after controlling for socio-demographic, health behaviours, and psychosocial variables. ‘Baptist’ men had, on average, a 1.3 higher BMI compared to those reporting no religious affiliation. Among women, ‘Non-Christians’ had, on average, a 1 unit lower BMI compared to those reporting no religious affiliation while ‘Other Christian’ women reported, on average, a 1 unit higher BMI. Our results also indicate that there was a negative relationship between religious importance and BMI among Australian women.