Marine debris is a global issue with acute impacts. Here, stakeholder interviews were combined with a quantitative analysis of debris to better understand the distribution and sources of marine debris in Belize. This study focused on seven islands off the southern coast of Belize and cataloged debris present using transects along each beach. Of the 1,754 items cataloged, the majority (68.1%) were plastics. The most commonly found items were plastic water bottles, glass bottles, and Styrofoam take-out containers. Once cataloged, debris was matched to an anthropogenic source, with the majority (74.8%) of sources being recreation-related. This source-based analysis provided insight into the causes of anthropogenic pollution in southern Belize. Conversations with stakeholders highlighted the importance of mitigating solid waste pollution in the local environment, and hence the need for an improvement in Belize’s waste management system. This research can inform Belize’s policymakers as they strive to bolster their tourist-driven economy.