Illegal cross-border fishing is an important maritime security issue in Southeast Asia. Southeast Asian states, along with other states with interests in the region, have created three new multilateral fisheries-relevant arrangements of agencies with overlapping but different memberships: the Regional Program of Action on Illegal, Unreported and Unregulated (IUU) Fishing; the ASEAN–Southeast Asia Fisheries Development Center Strategic Partnership; and the Coral Triangle Initiative. Each of these multilateral arrangements has the potential to help Southeast Asian states deal with fisheries-based security issues more effectively by building polycentric coalitions and capacity. So far, however, they have had a limited impact. This is partly because they are still principally technical support bodies rather than management organizations. In addition, states need to make greater strides towards settling outstanding border disputes and address fisheries overcapacity and overfishing in waters under their jurisdiction. States are unable to address these problems adequately because the fishery sector is typically low in national priority. Moreover, national interest in fisheries remains concentrated on immediate food and economic needs, and, in international relations, on jurisdictional rights.