Groundwater is the essential source of water and requires water quality protection to maintain ecosystems and socioeconomic growth globally. To date, aquifer systems are contaminated with heavy metals, metalloids, and microplastics (MPs) due to industry, urbanization, surface runoff from mulching garbage, and agriculture and food-related activities. In Bangladesh, floodplain aquifers receive precipitation and surface water recharge with MPs, heavy metals, and other contaminants due to horizontal and vertical transfer through soil. As a result, floodplain aquifers become the interim sinks for MPs, along with other pollution from anthropogenic activities posing a major risk due to the groundwater contamination. The book chapter reviews the existing knowledge of plastics in groundwater, examines the contamination mechanism of MPs and heavy metals in floodplain aquifers, and discusses MPs sources, distributions, and impacts on environment and human health due to groundwater pollution.