Under the concept of the ‘Blue Pacific’, island nations are placing increased priority on the oceans, seeking to integrate policy on climate change, maritime security, fisheries and ocean biodiversity. This agenda however affects France, one of the remaining colonial powers in the Pacific, which controls a vast maritime domain in the region. The 2016 decision to incorporate the French dependencies New Caledonia and French Polynesia as full members of the Pacific Islands Forum raises a series of diplomatic challenges for Forum island countries. This article outlines France’s interest in the Blue Pacific, in areas such as exclusive economic zones, security, research, climate and maritime boundaries. It then details problems facing Forum member countries arising from France’s ongoing control of its three dependencies in the region, including uncertainty over legal standing in the Forum; the capacity to sign treaties; policy making on security in the Forum; policy issues on fisheries and climate in other member agencies of the Council of Regional Organisations of the Pacific; relations with other Forum dialogue partners; resource exploitation by the colonial power; and disputes over maritime boundaries.