Abstract: Sumoylation is a newly discovered post-translational modification, in which a small ubiquitin-like modifier (SUMO) is covalently conjugated to a lysine residue in a target protein. This provides an efficient way to modulate the activity, stability and subcellular localization of a wide variety of substrates. Sumoylation plays a key role in the occurrence and development of type 2 diabetes mellitus (T2DM). This paper addresses the relationship between sumoylation and T2DM in regulation of pancreatic β-cell function, the metabolic order in skeletal muscles, liver and other organs and diabetes-associated complications. A deeper knowledge of sumoylation may enable us to better understand the pathogenesis of T2DM and sumoylation system at the molecular level, which can help provide new ideas for the early diagnosis and subsequent treatment of T2DM and its associated complications.