Following global trends, research to determine the presence and abundance of microplastics (MPs) in environmental matrices in Colombia has focused on the coastal and marine environments. However, little scientific information is available on the impact of this pollutant on wetlands and fish. In this study, we provided scientific data on the occurrence and abundance of MPs in water and fish from Tocagua Lake, an important wetland in the Colombian Caribbean, and the unique habitat of wild cotton-top tamarins (Saguinus oedipus). Water (72) and fish (228 individuals of six species) samples were collected during four sampling events and two climatic seasons (wet and dry). A total of 1174 microplastic particles were collected in water with an average abundance of microplastics at the six stations sampled during four sampling events of 0.96 ± 0.40 MPs/L, and 648 MPs were identified in the gastrointestinal tract of 191 individuals, corresponding to a frequency of occurrence of 83.7%. Black- and blue-colored fiber MPs were particles that predominated in both matrices (water and fish), and seven types of polymers were identified through attenuated total reflectance Fourier transform infrared spectroscopy analysis. The abundance, type, and color of MPs in water and fish were not significantly different between seasons.