Abstract: As an important source of new drugs, natural products exhibit extensive biological activities. However, most of them suffer from less potent activity, poor water solubility, and low bioavailability. Consequently, structural modification is needed to improve their druggability. Glycosylation is an important reaction for structural modification. Microbial transformation has the advantages of high selectivity, mild reaction conditions, and environmental friendliness. The recent progress in the field of glycosylation of natural products catalyzed by both whole cells and recombinant enzymes of microorganisms were reviewed.