Upon adoption of K-IFRS in 2011, Korean firms are required to disclose the existence of a major customer that account for 10 percent or more of the firm"s revenue (hereinafter CC). This study investigates the relationship between CC and the firm"s future stock price crashes. Further, we analyze whether the relationship between them is attenuated in case of family-controlled firms. Using the non-financial firms listed in KOSPI between years 2011 to 2017, we find that CC is positively associated with future stock price crashes. Further analysis reveals that the positive relationship between them is negatively moderated when the supply firms are controlled by family shareholders. Overall, the evidence suggests that the firms with a more concentrated customer-base are likely to withhold bad news, possibly leading to future stock price crashes. On the other hand, the positive relationship between them can be attenuated in family firms owing to their unique characteristics. Under the recent management paradigm shift from shareholder-capitalism to stakeholder-capitalism, the suppliers’ risk management can be an important issue for a firm’s sustainability. By providing the association between CC and suppliers’ future crash risk, this study may shed light on the practice of firm’s implementation of stakeholder-oriented management.