Knowledge sharing in higher institution of learning such as Universities is important to improved productivity. The purpose of this study is to analyse psychological motivations underlying non-academic staff’ knowledge sharing behaviour (KSB) in University of Ibadan using the theory of planned behaviour (TPB). A questionnaire survey was conducted among non-academic staff from 13 faculties in the University of Ibadan. A total of 276 usable questionnaires were collected. Multiple regression analysis is applied to test the research model and hypotheses. Findings from the study revealed that non-academic staff’ knowledge sharing intention is significantly influenced by attitude, subjective norm and perceived behavioural control. Also, perceived behavioural control was identified as the factor having the strongest influence on knowledge sharing intention. Furthermore, it was found that non-academic staff’ KSB in university of Ibadan is significantly predicted by their perceived behavioural control and knowledge sharing intention, signifying that KSB is under both non-academic staff’ volitional and perceived behavioural control, which is different from other groups of professionals in previous studies. Several managerial implications are suggested for the administrators to manage non-academic staff’ KSB in the university. It is one of the first studies to exploit social psychological theory to examine non-academic staff’ KSB in the university setting. 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, subjective norm and perceived behavioural control so as to explain KSB among non-academic staff’ in the university context.