Cardiac Autonomic Neuropathy (CAN) is a major chronic complications of DMII. Clinical investigations have revealed that uncontrolled DM II is frequently associated with lower levels of BDNF. This study assessed whether diminished BDNF level is the reason of CAN caused by DM II and if swimming aerobic exercise can increase BDNF level to ameliorate that CAN . Sixty rats were divided into six groups. Group I; Normal (N), Group 2; BDNF blocker, Group 3; DM II, Group 4; DM II + BDNF, Group 5; DM II + Swimming exercise and Group 6; DM II + Swimming exercise + BDNF blocker. Induction of DM II was done by intraperitoneal injection of 180 mg/kg of Nicotinamide 30 minutes before injection of 50 mg/kg Streptstozin. Swimming exercise began with a 1-week adaptation with gradual increase of swimming duration until reaching 1h swimming/day at the end of the 1st week. Then, a 7-weeks training program with 5 days/week swimming was followed. The duration of the experiment was 8 weeks during which the following parameters were measured: body weight, random blood glucose “RBG" level, plasma insulin level, heart rate “HR", systolic blood pressure “SBP", heart rate variability “HRV", baroreflex sensitivity “BRS", vascular sympathetic tone “VST" and plasma BDNF. Results revealed that BDNF significantly improved RBG level, HRV, VMT and BRS. Swimming exercise significantly increases plasma BDNF level and also improved CAN. Conclusively, BDNF can be used as a treatment regimen for CAN. Also swimming exercise has great therapeutic effect on CAN maybe by producing BDNF.