<p>The environmental impact of microplastic pollution has triggered the alarm of public for over 20 years. The South China Sea, situated as a marginal sea in the tropical region, is surrounded by unique blue-carbon ecosystems and densely populated provinces that produce a substantial amount of industrial plastic waste. Understanding the source-sink relationship and distribution of microplastics in rivers, nearshores, and estuaries is crucial for safeguarding the ecological integrity of estuarine environments. In this review, a comprehensive review of recent researches on the distribution and source-sink relationships of microplastics in rivers and nearshore and offshore regions in the South China Sea have been discussed. Due to atmospheric deposition and precipitation, microplastics exhibit spatial heterogeneity in terms of abundance and distribution in areas surrounding the South China Sea. The major pollution sources include river inputs, industrial wastewater discharge, aquaculture activities, and shipping operations. Anthropogenic and other biological factors such as fish ingestion and vegetation entrapment also affect the distribution and transport of microplastics. To quantify the abundance and distribution of microplastics and elucidate their transport mechanisms, it is recommended to strengthen the detection and management of microplastics in the South China Sea region, standardize sampling methods and units, establish shared databases, and explore effective governance pathways.</p>