The study empirically investigated how employees’ perception of interpersonal trust at work affects the extent to which they go beyond formally prescribed roles, Organizational Citizenship Behaviour (OCB). The survey design was employed for the study. Two dimensions of interpersonal trust at work (Trust in co-workers and trust in Management) and OCB were studied. Social Exchange Theory was utilized in describing potential relationships between trust and citizenship behaviour. Data were obtained from 152 employees randomly sampled from various organizations and analyzed using Pearson’s r and multiple regression analysis, and the hypotheses were tested at .05 and .01 levels. The major findings of the study suggested that employees’ interpersonal trust at work significantly influences their discretionary behaviour. A very vital finding was that employees’ trust in co-workers influenced their organizational citizenship behaviour more than their trust in management. Understanding personal and organisational factors associated with OCB have important implications for the training, and development of employees to facilitate the smooth operation of any organization. There is paucity of published studies in Ghana on how interpersonal variables, such as trust, affect employees’ work attitude and behaviour as well as organisational outcomes. This study is therefore very invaluable in providing insight into the Ghanaian context in this area.