This article contributes to the literature on transnational environmental governance (TEG). Polycentricity is a popular conceptual approach in TEG, but coordination in polycentric systems remains largely unexplored. We put forward a conceptual model of quality standards as a productive links between different orders of governance in polycentric systems. Existing theories distinguish between regulative, institutional, and normalizing functioning of quality standards. We develop an integrative approach highlighting the mechanisms of coordination that rely on these three functions of quality standards. The case of TEG in shipping is used to illustrate how quality standards function not only as soft rules, but also as institutionalized references and shared conventions, enabling coordination across levels and scales. The paper draws attention to the limits of regulatory standardization, outlining how practical value can be gained from emphasizing the normative work associated with promulgation of quality standards.