The complex metabolic, vascular and inflammatory perturbations that characterize diabetes mellitus often lead to progressive albuminuria, renal injury and dysfunction (diabetic nephropathy [DN]), and diabetes is the leading cause of end-stage renal disease in the US and Europe. Diet has an important role in cardiometabolic disorders and its potential influence on DN is of interest. Fatty acids are a major source of energy, but in excess, fatty acids (particularly saturated fatty acids) can induce lipotoxicity. Omega-3 polyunsaturated fatty acids (PUFAs) confer protection against cardiovascular disease-the major cause of death in patients with DN-by virtue of their antihyperlipidemic, antihypertensive, anti-inflammatory and other properties. Omega-6 PUFAs are also cardioprotective. However, a significant proportion of adults consume insufficient quantities of these essential nutrients. This Review describes the role of omega-3 and omega-6 PUFAs in nutrition and metabolism, with a focus on experimental, epidemiologic and clinical studies that have investigated their renoprotective effect in patients with diabetes. Results from a number of studies suggest, but do not firmly establish, that long-chain omega-3 PUFAs (found in fish oil) reduce albuminuria in the setting of DN. Intake of omega-6 fatty acids is associated with reduced albuminuria in experimental settings and in epidemiologic studies of DN. Although PUFAs do not seem to attenuate glomerular dysfunction, insufficient evidence exists to rule out such an effect. We feel that further research is needed into the potential of PUFA consumption and supplementation in DN.