The aim of this review was to discuss the current understanding of Type 2 Diabetes Mellitus (T2DM) genetic advance and aetiology. The T2DM is a genetically heterogeneous disease, with several relatively rare monogenic forms and a number of more common forms resulting from a complex interaction of genetic and environmental factors. Earlier studies using a candidate gene approach, family linkage studies and gene expression profiling uncovered a number of T2DM genes, but the genetic basis of common T2DM remained unknown. Recent years have seen a tremendous surge in our understanding of the genetics of T2DM by Genome-Wide Association Study (GWAS). Approximately 20 genes consistently associated with T2DM mainly implicate pancreatic β-cell function in the pathogenesis of T2DM.