This study contributes to the field of sustainable supply chain management by shedding light on the relationship between overdependence on supply chain partners, exploitation, and the willingness of business-to-business partner firms to focus on sustainability performance. This study further investigates how ethical culture moderates this relationship. Drawing on the resource dependency theory, the study involves developing a model and validating it using multivariate analysis among 120 dyads. The findings reveal that a business-to-business firm’s overdependence on its supply chain partners can lead to it being exploited, which in turn negatively impacts its willingness to prioritize sustainability within the supply chain. Moreover, the study demonstrates that the stronger the firm’s ethical culture, the weaker the effect of overdependence on exploitation, while at a lower level of the firm’s ethical culture, the effect of overdependence on exploitation is stronger. The utilization of resource dependency theory unveils the potential downsides of overreliance on business-to-business supply chain partners and its consequences within the supply chain.