As environmental, social, and governance (ESG) considerations face growing scrutiny in global markets, it becomes increasingly important to examine settings where ESG performance delivers measurable institutional value. This study investigates the role of ESG as a proxy for corporate trustworthiness in China's national drug procurement system - a high-stakes, rule-based environment in which supplier credibility is a formal eligibility requirement. Using data on Chinese A-share pharmaceutical firms from 2019 to 2024, we find that firms with stronger ESG profiles are significantly more likely to win tenders. Our results remain robust across alternative model specifications, bidder identification strategies, and methods addressing potential endogeneity. Event study analyses further show that procurement wins generate positive investor responses, reinforcing the strategic importance of such outcomes. Our findings highlight the operational relevance of ESG in public procurement and demonstrate that ESG-based trust signals can serve as a meaningful basis for firm evaluation where credibility is an explicit criterion. These insights carry global significance for policymakers, investors, and firms navigating government procurement in both emerging and advanced economies.