This study examines the association between customer base concentration and corporate public disclosure policy. When the customer base is more concentrated, large customers face lower costs of accessing the supplier firm's private information, reducing customers' overall demand for the supplier's public information, suggesting a negative association between customer concentration and the amount of public disclosure. Alternatively, large customers have greater bargaining power and may demand that the supplier firm provide more public disclosures. Consistent with customer concentration facilitating private information flow from the supplier to customers, we find that the frequencies of management earnings and sales forecasts are negatively associated with customer concentration among firms with major corporate customers. These associations are stronger when the supplier and customers are engaged in more relationship‐specific investments, when customers' private information acquisition costs are lower, and when it is less costly for customers to find another supplier.