This chapter provides an overview about the derivatives of chitosan using the green technology. It has demonstrated the functionalities of the chitosan. It has established the narrative that why the green derivatization is significant. It has discussed that chitosan specification depends upon isolation process and its source making it obligatory to know the intrinsic properties of chitosan and its impact on chitosan derivatives, whereas the biological and physicochemical properties of chitosan can be improved by its derivatization. It has provided a glimpse that the need of chitosan derivatives with enhanced properties, such as increased stability especially at basic and neutral pH values, can be useful for various applications. Moreover, chitosan derivatives with these enhanced properties can be used for therapeutic chemical delivery. It has discussed that number of qualities, such as solubility, hydrophilic character, affinity for bioactive compounds, and gelling capabilities, can be enhanced by the chemical derivatization of chitosan. The click chemistry has also played a key role in understanding the derivatization process in chitosan. In chitosan derivatization, cycloadditions are one of the most commonly waged reactions. The quaternary derivatives of chitosan have also been introduced in this chapter as an attractive, pliable, and functional polymer. The synthesis of these derivatives along with carboxymethyl chitosan has been discussed as well. It has also discussed the thiolated chitosan along with chitosan enzyme inhibitors. It has discussed how EDTA has been effectively used to modify chitosan-based adsorbents. The chapter has also provided the synthesis of half-acetylated chitosan, acrylated chitosan, glycol chitosan, chitosan catechol, Chi-C, and many more. It has provided a comprehensive analysis of the chitosan derivatization.