<p>Plastic pollution has emerged as a global environmental concern, threatening ecosystems worldwide. Coastal environments are particularly vulnerable, with aquatic biodiversity at significant risk. While many studies have explored the ingestion and toxicological impacts of plastic particles on organisms, gaps remain in understanding their long-term effects and organismal responses. In this study, we conducted a systematic review to assess the effects of plastic pollution on organisms residing in coastal marine ecosystems. After screening and eligibility assessments, 936 articles were included in the synthesis. We found an increase in publications over the past five years (2020—2025), with a predominance of observational studies (72.6%). Coastal areas, estuaries, and beaches were the most examined environments. Microplastics were the most reported particle size fraction, mainly composed of polyethylene and polypropylene in blue and green colors, originating from fishing gear, plastic bags, and bottles. The groups most frequently reported as affected were molluscs (n = 425), fish (n = 301), and crustaceans (n = 197). Key observed effects on the organisms included increased physiological damages, particularly related to ingestion and metabolic disruption. Despite ongoing efforts to limit its use, plastic remains widespread due to its low cost and versatility, highlighting the urgent need for institutional and governmental actions to mitigate its accumulation in the environment, especially in aquatic ecosystems.</p>