Can a small island state be sustainable? Small islands often suffer from a myriad of sustainability challenges owing to their remoteness, size, dependency on imports, and limited waste absorption capacity. Most imports end up as waste accumulation in dumpsites at the end of their life-cycle, representing a one-way material flow. The concept of the “circular economy” (CE) is a promising resource management strategy for island nations to improve solid waste management. In a CE, waste is a resource to be continually circulated within the economy. This study uses material flow accounting (MFA) to quantify waste deposits in Grenada, a tri-island, Caribbean state (population: 110,874). Like many Caribbean islands, Grenada has waste challenges as a result of accumulation of materials in open dumpsites and the persistence of illegal dumping. We estimated that Grenada generated 46,097 tonnes or 1.14 kgs per capita per day of waste in 2017. Leveraging disaggregated trade and waste data, we quantified three problematic waste streams: plastics, tyres, and motor oil and demonstrate an approach for conducting MFA in data-poor environments. Based on the results, Grenada has opportunities to decrease waste production by implementing circularity measures. We recommend improving data collection, implementation of the polluter pays principle, banning substitutable, problematic materials, and developing waste management plans for problematic materials. It is critically important that Grenada transition to a more sustainable waste management system in order to realize the vision of sustainable development. The results of this study make an important contribution to island industrial ecology and sustainable development.