<p>While the adverse effects of dependence on fairness have been extensively documented, the relationship between sellers’ platform dependence and their fairness perceptions in platform-based e-commerce remains intricate and potentially non-linear. Drawing on social exchange theory and conservation of resources theory, this study examines the underlying mechanisms through which seller platform dependence influences fairness perception, along with its boundary conditions. Particular attention is given to the cooperative relationships and specific interactions between platforms and sellers. Employing survey data from 302 respondents and rigorous evaluation metrics, the study utilizes moderated path analysis to test the proposed research hypotheses. The findings reveal that both fairness perception and voice behavior exhibit U-shaped relationships with seller platform dependence. Moreover, seller voice behavior not only positively affects fairness perception but also mediates the relationship between platform dependence and fairness perception. Notably, platform incentives and seller reputation exert contrasting moderating effects: while platform incentives attenuate the mediating role of seller voice behavior, seller reputation amplifies it. Furthermore, heterogeneity analysis indicates that the U-shaped effect of seller platform dependence on fairness perception is more pronounced on emerging platforms than on traditional ones and is more significant among larger sellers compared to smaller ones. These findings contribute to the literature on enterprise dependence by revealing its dual nature and provide theoretical insights for fostering fair and sustainable platform-seller relationships in the evolving e-commerce landscape.</p>