A pro-environmental behaviour to solve the problem of household waste and achieve sustainable municipal solid waste management is waste separation behaviour (WSB). As part of pro-environmental behaviour, WSB is argued to be influenced by rational decision-making approach (i.e. the theory of planned behaviour [TPB]) and moral norms approach (i.e. norm activation model [NAM]). Drawing from the integration of the TPB and the NAM along with the addition of a moderator i.e. ‘local government support’ as an external predictor of WSB, a new model was developed. Using structural equation modelling, this study tested the integrated structural model amongst 1697 household residents in the city of Joondalup, Australia. The SmartPLS results indicated that the personal norm, social norms and perceived behavioural control were found to be the major factors influencing residents towards WSB while both attitudes and local government support were unexpectedly found to have no significant influence thereon. Furthermore, the perceived behavioural control was found to have the highest effect on WSB. This indicates the more Joondalup residents feel confident and capable of sorting the waste at source, they will be more driven towards sorting their waste using the three-bin system. These findings are useful for promoting and planning WSB by policy-makers to ease the waste disposal problem.