Illegal, unreported and unregulated (IUU) fishing activities are widely considered a main cause of unsustainable fisheries across the globe. The EU has taken a leading role in the fight against IUU fishing, using both its market and normative power to advance its EU IUU Regulation (no. 1005/2008) and wider fisheries sustainability agenda outside its territory. This paper examines how successful the EU has been in using its market and normative power to influence regulatory strategies and frameworks governing tuna fisheries in the Pacific Islands region of the Western Pacific Ocean. The results indicate that while the market power of the EU remains an influential factor, the diminishing normative power of the EU in WCPO is weakening any attempts to implement its IUU fishing regulation and Pacific Island nations have promoted their own regulatory agenda. We conclude that the changing asymmetries between market and normative power has led to a differentiated geography of regulatory uptake, and while market power will remain a dominant strategy for the EU, normative power, when exercised should focus on cooperation rather than ‘teaching’ the benefits of an EU regulatory approach.