Gestational diabetes mellitus (GDM) is defined as abnormal glucose tolerance diagnosed for the first time during pregnancy. The pathogenesis of GDM is characterized by relatively reduced insulin secretion insufficient to meet the increased insulin demand, which is quite similar to that of type 2 diabetes mellitus. Thus GDM is considered to have a common genetic background as type 2 diabetes mellitus. However, only limited information is available for the genetic basis of GDM. In this review article, we will briefly discuss the definition, epidemiologic features, and pathophysiology of GDM. In addition, we will present the data of two recent genetic association studies regarding GDM. Most of the previously proven type 2 diabetes associated with single nucleotide polymorphisms were also associated with the risk of GDM. Rapidly increasing knowledge in genetics of GDM will generate new insights into the pathophysiology, treatment, and prevention of GDM.