With the increasing use and application of engineered nanoparticles (ENPs) in a number industries, ENPs, through their unique properties, have made their way into the environment. However, the environmental fate and behavior of ENPs are largely unknown. Laboratory studies have shown that some ENPs have the potential for toxicity, suggesting they may affect organisms in the environment. To fully assess the risk of ENPs, a better estimation of exposure concentrations is needed. This requires an understanding of the stability and toxicity of nanoparticles (NPs) in the environment. This review presents a brief overview of the fate, behavior, and ecotoxicity of NPs in the environment. The fate and transport of NPs, which can be affected by various environmental conditions like light, pH, ionic strength, and type and concentration of cations, are important for the examination of the life cycle of NPs.