The rapid increase of cases of type 2 diabetes mellitus (T2DM) in the past decades has made it a widespread metabolic disorder.  In addition to well-established risk factors for T2DM, including genetic predisposition, poor physical activity, fetal programming and obesity, an altered configuration of the microbial community in our gut – the microbiota – has emerged as a new candidate that may be linked to T2DM. The aim of this review is to focus the light on the role of gut microbiota as a novel key organ involved in metabolism, and discussing the putative mechanisms linking gut microbiota and T2DM, as well as the therapeutic perspective of intestinal microbiota modulation for T2DM.