Post-translational modifications (PTMs) play important roles in regulating protein stability, trafficking, folding conformation, and functional activity. Small ubiquitin-like modifier (SUMO) protein mediates a distinct type of PTM called SUMOylation in which the SUMO protein is covalently ligated to the target protein and modifies its activities through a series of enzymatically-catalyzed reactions. SUMOylation regulates many cellular processes like transcription, the maintenance of the ion gradient across the cell membrane, stress response, autoimmunity, etc. Several target proteins of SUMOylation are involved in the biological pathways related to various human diseases, including cardiovascular diseases, diabetes, cancer, and neurodegenerative disorders. This review focuses on the SUMOylation process, regulatory roles of SUMOylation in diabetes, and prospects of developing novel anti-diabetic drugs targeting the SUMOylation process.