The 26,530 ha Peel-Yalgorup System near Mandurah Western Australia is one of the largest and most diverse Ramsar-listed wetland systems in Australia, incorporating the Peel Inlet and the Harvey Estuary (the Peel-Harvey Estuary), the hypersaline Yalgorup Lakes and the freshwater lakes McLarty and Mealup. The wetland system meets at least seven of the nine criteria for listing according to the Ramsar Convention as a ‘wetland of international importance’ and was recognised as Ramsar Site 482 in 1991. These values are threatened by the rapidly growing urban population of Mandurah and inappropriate land-use practices. Without action these threats will continue unabated, potentially compromising the site’s Ramsar listing. Here we present a case study of action taken by the community to prevent a major threat to the values of Ramsar 482. The Point Grey peninsula sits at the intersection of the Peel Inlet and the Harvey Estuary opposite to the Dawesville Channel. Urban development of the peninsula was first proposed in 1988, prior to the listing of the wetlands as Ramsar 482. At that time the Environmental Protection Authority (EPA) recommended that the development should not proceed due mostly to the ecological value and fragility of the estuarine ecosystem. Fast-forward to 2011, when a development of 275 ha of the site was proposed, involving the construction of a 330-berth on-shore marina, a 2.5 km long navigation channel connecting the marina to the estuary and the Dawesville Channel and a residential community with more than 3000 home sites. After assessment by the EPA, the Point Grey Marina Development was approved by the WA Minister for the Environment. Due to the environmental significance of Ramsar 482, a number of organisations, including the Peel-Harvey Catchment Council (PHCC) and the wider community raised concerns about the potential impact of the development proposed Point Grey Development, in particular on the Peel-Harvey Estuary. Of greatest concern were the impacts on the aquatic environment of dredging operations to construct the navigation channel, the disposal of dredge spoil from the dredging works, the likely accumulation of monosulfidic black ooze in the navigation channel and marina and the subsequent maintenance dredging and spoil disposal operations. The loss of native vegetation and habitat through excavation and dredging to construct the on-shore marina was also concerning. Because of the Ramsar listing of the estuary and the Australian Government’s obligations to protect the site under the EPBC Act, the development was referred to the Australian Government for assessment. Despite community concerns including expert opinion of the unacceptable risks the development posed to the Peel-Harvey estuary, in 2014 the Australian Government granted Ministerial Approval for the development valid until 2052, albeit conditional. This case study describes the ongoing struggle by a concerned community in resisting the Point Grey Marina development to protect the ecological values of the Ramsar 482 site. It demonstrates how Ramsar listing by itself does not provide sufficient protection for wetlands of international importance without an engaged and well-informed community using scientific evidence to underpin its arguments to influence decision makers.