Recently the potential of genetically engineered silkworms (Bombyx mori) to work as “biofactories” for the production of recombinant proteins has gained a great deal of attention. Pharmaceutical proteins are usually post-translationally modified under the host-dependent modification potetial. Fundamental information on glycosylation in silkworms facilitate to understand the potential of insect production of pharmaceutical proteins. In this chapter, the potential of glycosylation in silkworms is described. In addition, this chapter discussed development of production of recombinant proteins with engineered N-glycans.