Biotransformations are chemical reactions catalyzed by cells, organs or enzymes and represent an area of biotechnology that has received considerable attention. The use of biotransformations with plant cell culture systems and fragments of plant tissue has immense potential for the production of compounds with commercial interest, especially considering the vast biochemical capability for the production of secondary metabolites from plant sources. In this context, this chapter evaluates the application of biotransformations in different plant cell culture systems, such as cell suspensions, hairy roots and cell immobilization, as well as fragments of plant tissue.