Purpose: This paper aims to develop an understanding of the factors that influence knowledge-sharing behaviour within an organisational framework, using widely accepted social psychology theories. Design/methodology/approach: Knowledge-sharing behaviour of bank employees in Greece is examined using an aggregate model, which is based on the theory of planned behaviour. The suggested research model was tested using structural equation modelling. Findings: The results indicate that intention to share knowledge is mainly influenced by employees' attitude toward knowledge sharing, followed by subjective norms. Research limitations/implications: Knowledge-sharing behaviour was examined solely focusing on salient beliefs. Findings should be confirmed using a larger sample, as well as through cross-sectional studies. Practical implications: The results highlight the necessity of creating a climate that would help individuals develop a more favourable attitude toward knowledge sharing as well as the important role of the perceived social pressure by organisational members (peers, supervisors, senior management) on the intention of individuals to share knowledge. Originality/value: The main contributions of this study are the following: examination of the knowledge sharing in the banking sector; testing of a specific well-known research model in the South-Eastern European environment; examination of the actual knowledge-sharing behaviour and not only of the behavioural intention to share knowledge and, finally, examination of the direct effect of the perceived behavioural control on knowledge-sharing behaviour, which, although suggested by theory, has been neglected by previous studies.