Non-Alcoholic Fatty Liver Disease (NAFLD) is a clinical condition caused by excessive accumulation of triglycerides (TG) within hepatocytes. NAFLD is recognized as the leading cause of chronic liver disease in adults and children worldwide. It is associated with obesity and diabetes and mostly closely linked to insulin resistance. Scientific investigation into NAFLD pathogenesis has increased exponentially in the last years. Main pathways include (i) increased visceral adipose tissue and insulin resistance, (ii) altered hepatic fatty acid export, oxidation, and desaturation within the liver and (iii) the initiation and subsequent effects of lipotoxicity. Altered hepatic glycerol import is also a major intersecting component; however, the underlying mechanism has begun to be clarified only recently after AQP9, an aquaglyceroporin regulated by insulin and leptin, was found to mediate the liver uptake of glycerol. AQP9 is downregulated post-translationally in the liver of morbidly obese patients with NAFLD associated with insulin resistance and diabetes (T2DM) and in animal models of NAFLD. The decrease in AQP9 expression and consequent reduction of glycerol influx into hepatocytes is thought to be a compensatory mechanism to avoid further TG infiltration in liver parenchyma. AQP9 is a new player in metabolic homeostasis and may prove a novel target to treat NAFLD, a common feature of metabolic syndrome.