This study examined an extended theory of planned behaviour (TPB) model that specified factors affecting students' intentions to collaborate online for group work. Past behaviour, past experience and actual behavioural control were incorporated in the extended TPB model. The mediating roles of attitudes, subjective norms and perceived behavioural control were also examined. Data were collected from primary and secondary students in Hong Kong (N = 957). The partial least square approach to structural equation modelling was used to analyse the "a priori" hypothesised model. In general, the model fitted the data very well and the major relationships were found to be significant. The results indicated that past experience and actual behavioural control played individual roles in the model. Theoretical and practical implications are considered in this study.