Abstract: In general, the major customers and suppliers of enterprises are regarded as two independent entities, however, what impact will it have on the resilience of a company’s supply chain if a major customer also serves as a supplier? Taking China’s A-share listed firms from 2009 to 2021 as samples, this paper explores the impact and mechanism of the major customer also serving as a supplier on firms’ supply chain resilience. The findings show that the major customer also serving as a supplier can significantly reduce the supply chain resilience, and the negative media coverage will exacerbate this effect, while trade credit supply and effective internal control can mitigate this damaging effect. The mechanism analysis reveals that due to the fact that it is more convenient for enterprises to engage in related party transactions and promote their earnings management behavior, serving as a supplier by a major customer can further reduce the resilience of the enterprise’s supply chain. The analysis of economic consequences shows that due to the fact that serving as a supplier by a major customer can reduce the resilience of a company’s supply chain, serving as a supplier by a major customer can increase the company’s financial difficulties, reduce its market value, and increase the likelihood of receiving non-standard audit opinions. To this end, it is necessary to strengthen the supervision of the major customers who also serve as suppliers, so as to curb the opportunistic behaviors of the major customers who also serve as suppliers.

Key words: major customers-suppliers duality, supply chain resilience, supply chain risks