Although it is a well-established fact that dietary fish oil can improve nerve conduction velocity in diabetic rat, but the exact mechanism of its action is unknown. Therefore, in this study we measured the blood glucose level of all animals for evaluating the possible effect of fish oil in improvement of nerve conduction velocity in diabetic neuropathy via regulation of blood glucose level. For this purpose, 30 male albino rats were randomly assigned to one of the three treatment protocols as follows: control, diabetic and fish oil groups. Blood glucose of animals was determined in all groups at the beginning and at different days after the experiment. Diabetic and fish oil-treated diabetic groups received alloxan (180 mg/kg, s.c.) at the beginning of the experiment. Animals with blood glucose higher than 300 mg/dl were considered diabetic. From the 10th day, Menhaden fish oil was used (by 10% of daily food consumption) through orogastric tubing for ten days. After 20 days, motor nerve conduction velocity (MNCV) of tibial nerve was measured. It was found out that there was a 17.1% (P<0.01) reduction in MNCV of diabetic group in comparison with control group. There was also a 6.5% (P<0.05) increase in MNCV of fish oil-treated diabetic group in comparison with untreated-diabetic group. Results also showed that there were no significant differences between the groups regarding blood glucose level. On this basis it can be concluded that pretreatment of diabetic rats with fish oil does not act through changes of blood glucose level, and it may act through other unknown pathways.