Within fisheries and natural resource management literature, there is considerable discussion about the key roles that property rights can play in building biologically and socially sustainable resource management regimes. A key point of agreement is that secure long-term property rights provide an incentive for resource users to manage the resource sustainably. However, property rights mismatches create ambiguity and conflict in resource use. Though the term mismatches is usually associated with problems in matching temporal and spatial resource characteristics with institutional characteristics, I expand it here to include problems that can arise when property rights are incompletely defined or incompletely distributed. Property rights mismatches are particularly likely to occur over marine resources, for which multiple types of resource and resource user can be engaged and managed under a variety of regulatory regimes. I used New Zealand's marine resources to examine the causes and consequences of these property rights mismatches. New Zealand is particularly interesting because its property-rights-based commercial fishing regime, in the form of individual transferable quotas, has attracted considerable positive attention. However, my review of the marine natural resource management regime from a broader property rights perspective highlights a series of problems caused by property rights mismatches, including competition for resources among commercial, customary, and recreational fishers; spatial conflict among many marine resource users; and conflicting incentives and objectives for the management of resources over time. The use of a property rights perspective also highlights some potential solutions such as the layering of institutional arrangements and the improvement of how property rights are defined to encourage long-term sustainability.