Knowledge sharing in construction teams is important for improved project performance and successful project delivery. The purpose of this study is to analyse psychological motivations underlying individual knowledge sharing behaviour in Hong Kong construction teams using the theory of planned behaviour (TPB). A questionnaire survey was conducted among professionals from 172 construction companies in Hong Kong. A total of 231 usable questionnaires were collected. Structural equation modelling (SEM) is applied to test the research model and hypotheses. The research results indicate that professionals’ knowledge sharing behaviour in construction teams is only significantly predicted by their intention to share knowledge rather than perceived behavioural control over knowledge sharing, implying that knowledge sharing behaviour is largely under the professionals’ volitional control. The research results also indicate that professionals’ knowledge sharing intention is dominantly affected by attitude and perceived behavioural control but weakly influenced by subjective norm, which is different from other groups of professionals in prior studies. Several managerial implications are suggested for construction companies to manage employees’ knowledge sharing behaviour in construction teams. It is one of the first studies to employ social psychological theory to examine knowledge sharing behaviour in the construction context. However, the research model only shows predictive power and lacks explanatory power. Nevertheless, it provides a starting point for future researchers to further explore the salient beliefs underlying attitude and perceived behavioural control so as to explain knowledge sharing behaviour in the construction sector.