Microplastics (MPs) have emerged as a pervasive environmental pollutant of global concern due to their persistence, small size, and ability to disperse across ecosystems. While research on MPs has advanced considerably in aquatic environments, terrestrial systems—and especially wild mammal species—remain largely understudied. This systematic review compiles and analyzes 19 studies published between 2021 and mid-2025 that investigated the occurrence of MPs in the feces of wild terrestrial mammals. For each study, data were extracted on host species, geographic location, sampling effort, quantification metrics, and laboratory methodologies. Current evidence reveals strong geographic biases, with most studies concentrated in a few countries, while entire regions such as Central America, Africa, and Australia, as well as subregions like Central Asia and the Middle East, remain unrepresented. MPs were detected in 41 mammal species from 12 taxonomic orders, though both taxonomic and spatial coverage remain limited. Analytical procedures commonly included drying at ≥40 °C, sieving, and chemical digestion, with microscopy as the predominant identification technique. Hydrogen peroxide, ethanol, and potassium hydroxide were the most widely used reagents. Quantification metrics varied markedly among studies, hindering comparability. As this research field continues to expand, developing standardized, transparent, and reproducible protocols will be essential to generate reliable and policy-relevant data on terrestrial MP contamination.