Water-soluble synthetic polymers (WSPs) are distinct from insoluble plastic particles, which are both critical components of synthetic polymers. In the history of human-made macromolecules, WSPs have consistently portrayed a crucial role and served as the ingredients of a variety of products (e.g., flocculants, thickeners, solubilizers, surfactants, etc.) commonly used in human society. However, the environmental exposures and risks of WSPs with different functions remain poorly understood. This paper provides a critical review of the usage, environmental fate, environmental persistence, and biological consequences of multiple types of WSPs in commercial and industrial production. Investigations have identified a wide market of applications and potential environmental threats of various types of WSPs, but we still lack the suitable assessment tools. The effects of physicochemical properties and environmental factors on the environmental distribution as well as the transport and transformation of WSPs are further summarized. Evidence regarding the degradation of WSPs, including mechanical, thermal, hydrolytic, photoinduced, and biological degradation is summarized, and their environmental persistence is discussed. The toxicity data show that some WSPs can cause adverse effects on aquatic species and microbial communities through intrinsic toxicity and physical hazards. This review may serve as a guide for environmental risk assessment to help develop a sustainable path for WSP management.