This research examines the impact of psychological contract breach (PCB) and organizational climate (OC) on the affective commitment and the effect of commitment on the proactive work behaviour of employees in four different sectors of Karachi, Pakistan. The study looks into affective commitment as performing the role of a mediator in linking PCB and climate with proactive work behaviours. The research also observes the moderation of tenure between the two links. The model is evaluated through Confirmatory Factor Analysis (CFA) and Structural Equation Modelling (SEM) through AMOS. In Pakistan, no such research has been taken up to observe the links between situational and psychological antecedents with proactive behaviour of employees. The present research makes an effort to fill this gap. Results of the research indicate that psychological contract breach (PCB) is inversely related to affective commitment while positive influence exists between organizational climate and affective commitment. Also affective commitment has a direct positive influence on proactive work behaviours. Psychological contract breach has full mediation while organizational climate has partial mediation effects on proactive work behaviour through affective commitment. Besides these variables, tenure also turned out to be a strong moderator of these links and thus moderated mediation tend to occur in the data set, the model is a good fit and it is significant. The findings support affective commitment as the mediator in the relationships between psychological contract breach, organizational climate with proactive work behaviour. The results provide guidelines and significant implications to help top managers and HR department to better understand and critically look into the current organizational climate and psychological contract created between the immediate manager and subordinate for increasing affective commitment and subsequently increasing proactive work behaviours. Furthermore, this study helps inEffect of Moderated Mediation on Proactive Work Behaviours 7 enriching the current body of knowledge on proactive behaviours in developing countries. Future studies should examine other antecedents like organizational citizenship behaviour and perceived organizational support to have a holistic approach. Replication of this study in other settings is also suggested.