The wide application of engineered nanoparticles (ENPs) in industries, biomedical fields, and personal care products has resulted in their inevitable release into the natural environment, thereby causing soil and groundwater contamination. ENPs are found to cause adverse health impacts on humans and the ecosystem. Hence, it is imperative to understand the transport pathways and associated retention mechanisms of ENPs in the subsurface to safeguard the drinking water sources from contamination and reduce potential impacts on the ecosystem. In this chapter, we discuss the transport pathways and retention mechanisms of the four most widely used ENPs such as TiO2, GO, ZnO, and CuO nanoparticles, the various factors affecting their transport behavior, and their interaction with soil microorganisms, and the need for further research. © 2023 Elsevier Inc. All rights reserved.