AbstractWe examine the association between a firm's cost of capital and its voluntary and mandatory disclosures. We include two types of mandatory disclosure: those that are a function of periodic reports that are realizations of ex‐ante reporting systems and those that arise due to specific corporate events. To capture a firm's voluntary and event‐driven mandatory disclosures, we use information the firm provides via 8K filings. To capture periodic mandatory disclosures, we use earnings quality measures derived from the literature. Consistent with endogenous relations predicted by theory, we find that voluntary disclosure and both types of mandatory disclosure are correlated, although only event‐driven mandatory disclosures are significant in models that explain voluntary disclosure. We also find that the cost of capital is generally influenced by each of these disclosure types. We also find that controlling for periodic mandatory disclosure does not affect the relationship between voluntary disclosure and the cost of capital, while controlling for event‐driven mandatory disclosure sometimes affects the relationship depending on the measures used. Our study suggests that a firm's disclosure environment includes the three types of disclosure examined, although the inclusion of mandatory disclosures does not affect the measured association between voluntary disclosure and the cost of capital.