Microplastics (MPs) are emerging pollutants in environmental media that scholars worldwide have been widely concerned about. MPs in terrestrial ecosystems are transported through runoff to other freshwater systems and oceans and are widely distributed in water bodies and sediments. Owing to limitations in detection technology, complexities in sampling, and high research costs, research on MPs in sediments is relatively scarce, with existing research mainly focusing on the occurrence characteristics of MPs in water bodies. There is a need to assess the contamination levels of MPs in sediments and their potential impacts on benthic organisms and ecosystems by studying microplastics in sediments, investigating the mechanisms of migration and transformation of microplastics in sediments, and supporting the development of effective strategies for pollution prevention and control. On this basis, the present article deeply reviews the research progress on the sources, occurrence characteristics, and ecological effects of MPs in sediments, analyzes the impacts of MPs in different sedimentary environments, summarizes issues that need to be addressed, and looks forward to future research directions, to provide a theoretical reference for subsequent pollution control and risk assessment of MPs in sediments.