Lignin is one of the major chemical components that can be found in plants. It gives rigidity and acts as a natural binder to plants. It can be extracted from lignocellulosic biomass using a range of extraction methods; thus, the lignin characteristics and chemical structure vary greatly depending on the method utilized. The lignin structure is complex owing to its content. Many functional groups with the reactive ones come from hydroxyl and phenolic groups. For this reason, their polarity needs to be modified in order to be used or blended with different materials, especially with other polymers. The lignin functional groups can be functionalized using various methods, most commonly through esterification. Esterification of lignin is carried out by functionalizing the hydroxyl group in order to increase its reactivity and correspond with the needs or specifications for further use, particularly when lignin is combined with other polymers. Therefore, within this chapter the esterification method of lignin is discussed, before being utilized in different applications.