Polysaccharide derivatives have attracted attention as sustainable and renewable sources of bioactive compounds. This review presents recent studies on the derivatization techniques and the biological properties of polysaccharide derivatives, including sulfated-, acetylated-, phosphorylated-, carboxymethylated-, aminated-, benzyolated-, C-glycosylated-, hydroxypropylated- and selenized-polysaccharides. The introduction of a new functional group(s) to native polysaccharides altered their physical, chemical, and most especially biological properties. Biological properties of polysaccharide derivatives depend on the molecular weight, type of modification, type of native polysaccharide, modification process conditions, solubility, and conformation. However, certain derivatives of some polysaccharides and hybrid derivatives (with multiple functional groups) have received less attention. Intentionally, derivatives of well-known polysaccharides (cellulose, starch, heparin, chitin, and chitosan) have been excluded from this review.