This study tested the mediating role of violation in the relationship between breach and both affective and continuance commitment and the extent to which this mediating role is moderated by exchange imbalance amongst a sample of 103 sales personnel. Results suggest that violation mediated the relationship between breach and commitment. Also, results suggest that perceived exchange imbalance moderates this mediating pathway: Low exchange imbalance increases the mediating role of violation in the case of affective commitment. On the other hand, exchange imbalance failed to moderate the mediating influence of violation in the case of continuance commitment. Results are discussed in view of the importance of a) including both measures of violation and breach in future studies and b) the role of social exchange in explaining psychological contract violation. (Contains 3 tables and 2 figures.)