This study identifies the channels linking internal and external stakeholder engagement to organizational capabilities for achieving corporate sustainability by analyzing the effects of third-party sustainability assessments. Drawing on social identity and signaling theories, we investigate the role of environmental, social, and governance (ESG) rating agencies as information intermediaries in corporate sustainability. Specifically, we examine the role of ESG ratings on the relationship between employee-oriented CSR practices and organizational capabilities, while focusing on equal opportunity in the workplace (EO) and work–life balance (WLB), using total factor productivity (TFP)Total factor productivity (TFP) and firm-level innovation output as proxies for organizational capabilities. Our findings reveal that ESG ratings influence organizational capabilities through a direct effect on investor trust and an indirect effect on employees’ social identity by particularly enhancing the effect of WLB on organizational capabilities. These findings offer significant implications for corporate managers to expand the dimensions of stakeholder engagement and highlight the need for market players to confirm ESG rating agencies’ roles as intermediaries while demanding transparency and accountability.