Microplastics (MPs) and nanoplastics (NPs) are ecotoxicological threats because they are able to accumulate and transport toxic metals, persistent organic pollutants or pharmaceuticals products. Consequently, NP pollution is also a public health problem. MP and NP particles arise into surface water bodies and sea water through two major routes: 1) by the transport in the marine environment as synthetic microbeads or microparticles (for example, incorporated into cosmetic products, or during the washing of synthetic clothes) and 2) by the fragmentation of large plastic debris into MPs and NPs, through ultraviolet (UV) photodegradation, biodegradation, mechanical and chemical degradation processes (secondary microplastics). Even if, interest of the scientific community in environmental pollution caused by MP and NP started at the beginning of the 21st century, the research works for reducing and/or removing 2 them in water is very recent. The objective of this chapter is to present the main methods of treatment or removal of MPs and NPs from water, as well as the processes under development.