Despite the crucial role of fairness in establishing and maintaining interfirm trust, the literature on how asymmetric perceptions of fairness affect mutual trust over time is limited. Adopting a dyadic view, this study investigates the impacts of fairness asymmetry on changes in mutual trust in marketing channel relationships. We further suggest that fairness asymmetry inhibits supplier performance through the mediating role of changes in mutual trust. With a two-wave sample of 239 buyer–supplier dyads, our study demonstrates that fairness asymmetry leads to a decrease in mutual trust over time, which in turn reduces supplier performance. Moreover, joint asset specificity weakens, whereas market uncertainty and behavioral uncertainty aggravate the negative effect of fairness asymmetry on buyer–supplier mutual trust. Our work offers fresh insights into the implications of fairness in ongoing buyer–supplier relationships and guidelines for practitioners to better manage their channel partnerships.