As one of the most biodiverse ecosystems providing critical ecological services, coral reefs are now increasingly exposed to microplastics (MPs), an emerging contaminant of concern that pervades freshwater and marine environments. This study presents a comprehensive analysis of the distribution patterns of MPs in coral reef regions and their ecological effects on coral holobionts. The results demonstrate that MPs are globally prevalent in coral reef ecosystems, with sources encompassing land-based inputs, tourism, and fishing activities, and have been detected in seawater, sediments, and biota. Fibers constituted the predominant morphological type, while polyethylene and polyethylene terephthalate were the primary polymer components. In terms of ecological effects, MPs induced oxidative stress, immune activation, and metabolic disruption in corals, impaired the coral–Symbiodiniaceae symbiosis, and acted synergistically with elevated temperature, ocean acidification, heavy metals, and antibiotics to exacerbate coral bleaching and tissue necrosis. This review provides a systematic understanding of MPs contamination patterns and toxicological effects in coral reef ecosystems, and offers a reference for future research and conservation management.