Type 1 diabetes mellitus is related to the vascular oxidative and nitrosative stress, the trigger for atherosclerosis and cardiovascular complications. The effects of moderate swimming training associated with quercetin oral administration were evaluated in aorta of rats with experimentally induced type 1 diabetes mellitus (T1DM), by analysing the nitric oxide-endothelial dependent relaxation (NO-EDR). T1DM rats received daily quercetin 30 mg/kg and followed the protocol of 5-weeks swimming exercise (30 min/day; 5 days/week). Aorta relaxation to acetylcholine (Ach) and sodium nitroprusside (SNP) were measured at the end of the experiment. Ach-induced endothelial dependent relaxation was significantly decreased in phenylephrine (PE) pre-contracted aorta of diabetic rats. Swimming exercise with quercetin administration preserved Ach-induced EDR but did not have any impact on SNP-induced endothelium-independent relaxation in the diabetic aorta. These findings suggest that quercetin administration associated with moderate swimming exercise could improve the endothelial NO-dependent relaxation in the aorta of rats with experimentally induced type 1 diabetes mellitus, showing that this therapeutical combination may improve and even prevent the vascular complications that occur in diabetic patients.