How international are international commercial courts (ICommCs)? Among lawyers, the notion of international courts (ICs) comes with a strong public international law connotation. This chapter traces examples of hybridity in international adjudication, focusing particularly on the admixing of domestic and international judicial forms, practices and legal cultures. More specifically, we focus on three core forms of hybridity in relation to ICs and ICommCs: professional, institutional and legal. After surveying a number of past and current ICs, we argue that hybridity is not a phenomenon only found in domestic international courts, but also a feature of many ‘proper’ ICs. We find that all three forms of hybridity are found at both ICs and ICommCs, which suggests that these – at first glance distinct forms of transnational adjudication – are in fact converging on a number of levels.