Polymers represent a critical category of excipients employed in contemporary pharmaceutical technology, significantly contributing to the formulation of therapeutic dosage forms. Cellulose derivativesCellulose derivatives exhibit distinct physicochemical properties, including swellability, viscosity, biodegradability, pH sensitivityPH sensitivity, and mucoadhesionMucoadhesion, which influence their application in the formulation of diverse dosage forms. Biocompatible, biodegradableBiodegradable polymers, and bioavailable excipients, notably celluloseCellulose and its derivatives, are crucial for drug delivery systemsDrug Delivery Systems (DDS). These materials have been extensively researched for their distinctive encapsulating and binding capabilities, along with their ecologically sustainable attributes. They are often employed in continuous or regulated medication delivery systems. Cellulose and its derivatives typically modify the solubility and gelling properties of pharmaceuticals, resulting in diverse approaches to control drug release profiles. This chapter offers a brief summary of what is currently understood about the chemistry and structure of common cellulose derivativesCellulose derivatives and their use in drug delivery systemsDrug Delivery Systems (DDS). The development of new cellulose-derived materials for sustained drug deliverySustained drug delivery, such as micro-celluloseCellulose (MC) and nano-cellulose (NC)Nano-Cellulose (NC), is also addressed.