["Business Strategy and the Environment, EarlyView. ", "\nABSTRACT\nThis study examines how sustainability performance is translated into sustainability disclosure under peer‐based isomorphic pressures and how such disclosures are valued in capital markets. Using 2016–2023 panel data from 647 Japanese‐listed firms, we analyze the triadic relationship between sustainability performance, sustainability disclosure, and market value, drawing on voluntary disclosure, legitimacy, and institutional theory. The results show that sustainability performance is positively associated with sustainability disclosure, while disclosure is also strongly conditioned by peer disclosure within industries, indicating pronounced isomorphic pressures. However, the translation of sustainability performance into disclosure is significantly weaker among firms with sustainability performance below the industry average, for which performance improvements translate into little or no change in disclosure. By contrast, the association between sustainability disclosure and market value does not vary systematically with firms' relative sustainability performance. Overall, the findings reveal an institutionalized disconnect between the generation and valuation of sustainability disclosure under isomorphic pressures.\n"]