In recent years, nanotechnology has played an important role in our lives, assisting us in different situations. Various incurable diseases such as cancer, diabetes, and hepatitis can be controlled by some nano-additives in their traditional drugs. Also, nanotechnology can lead us to increase the efficiency of different drugs and reduce the treatment costs in an unbelievable way. Due to their significant properties in different fields, such as biomedical, electrical, optical, and mechanical applications, they have attracted all the attention. In this category, nanofillers, with incredible behavior, have improved the properties in every single field, by enhancing their applications. Nanofillers have a wide range of benefits in biomedical fields as a motive for controlling the drug release rate, cell viability, sensitivity to pH, and temperature, as well as wound healing and bone regeneration. In this chapter, nanofillers and nanocomposites will be introduced and, as a brief, their applications in drug delivery systems will be discussed.