Pacific Island Countries and Territories are heavily reliant on fisheries for food security and livelihoods. However, marine pollution, including microplastic contamination, poses an increasing threat. Microplastics, plastic particles smaller than 5 mm, are widespread across marine ecosystems, raising concerns about their potential to negatively impact organisms that consume them and humans. This study provides the first dataset documenting microplastic ingestion across coastal fish species from three fishing communities on Tongatapu Island in the Kingdom of Tonga. A total of 139 fish from 33 species were sampled between November 2023 and March 2024. Microplastics were detected in 58 individuals, resulting in a frequency of occurrence of 42%, and an average load of 0.77 ± 0.10 MPs/individual. Fibers were found to be the most dominant form (71%), followed by fragments (21%) and films (8%). Polymer analysis revealed polypropylene and polyethylene as the most common materials. The results highlight species-specific differences in microplastic ingestion, suggesting varying exposure risks based on feeding behavior and habitat. This baseline dataset offers crucial insights into microplastic contamination in Tongan coastal ecosystems and establishes a foundation for future research. Continued monitoring is essential to assess the long-term impacts of microplastic pollution on marine biodiversity, food security, and human health, informing national and regional conservation strategies across the Pacific.