This chapter addresses the harmonization of trademark laws, both substantive law and administrative procedures, within different regional organizations. The topic of regional harmonization and procedural integration of laws is relevant in today’s geopolitical and economic framework considering the importance of trademarks for regional trade as well as the relevance of regional organizations as alternative fora for advancing trade and intellectual property (IP)-related negotiations instead of (or in addition to) multilateral negotiations at the World Trade Organization (WTO) and the World Intellectual Property Organization (WIPO). In particular, this chapter compares four distinct regional organizations in order to highlight different levels of regional harmonization and cooperation in these areas – from full harmonization, including the establishment of supranational rights and supranational institutions ruling on the interpretation of national and regional laws, to less integrated approaches based on the cooperation of national or regional offices regarding trademark registrations, and related administrative procedures.