This study aimed at providing explanation and prediction of principals' inclusive education intentions and practices under the framework of the Theory of Planned Behaviour (TPB). A sample of 209 principals from Hong Kong schools was surveyed using five scales that were developed to assess the five components of TPB: attitude, subjective norm, perceived behaviour control, intention, and behaviour. Rasch analysis was utilised to examine the psychometric quality of the scales and generate principals' measures, which were subsequently subjected to path analysis to investigate the relationships among the five components. The results revealed a good model-data fit. Principals' attitude and perceived subjective norm were strong and significant predictors of their intention to implement inclusive education. The predictive power of perceived behaviour control on intention was not significant. Intention and perceived behaviour control were found to have significant predictive power for principals' reported inclusive practice. The implications of the findings are discussed.