Background: Type 2 diabetes (T2D) is considered “the epidemic of 21th century” affecting approximately 347 million people worldwide. It’s rapidly increasing global prevalence is a primary cause of concern. Homocysteine (Hcy) is a sulfur containing amino acid [COOHCH (CH2CH2SH) NH3]. Mild homocysteinemia is an independent risk factor for atherosclerosis, atherothrombosis and may even increase the risk of cardiovascular disease (CVD) in people with T2D. There is a low prevalence of diabetes in Greenland and Alaskan Eskimos, populations as known for a very high intake of N-3 polyunsaturated fatty acids (n-3 PUFAs). High intake of n-3 PUFAs have potential antiatherosclerotic effects and also reduce deaths from CVD.In recent years, several studies have been implemented about n-3 fatty acids, but none of them have been able to completely show its effects on diabetes patients. This study has been conducted to determine the effects of n-3 PUFAs supplementation on Hcy level, lipid profile and insulin resistance in patients with T2D.Methods: This study is a double-blind controlled trial involving 70 patients with T2D selected from Yazd Diabetes Research Center in 2013. Patients were randomly assigned to receive either 2 g/day omega-3 soft gels (OG) or 2 g/day placebo (PG) for 6 weeks. At the beginning and end of the study, Hcy concentration, fasting plasma glucose, fasting plasma insulin, total cholesterol, triglycerides (TG), LDL-c, HDL-c, HDL-c/LDL-c ratio, insulin resistance (HOMA-IR), insulin sensitivity and beta-cell function was measured and compared.Results: Sixty five participants completed the study.N-3 PUFAs supplementation caused significant increase in Hcy level compared in OG with PG, but there was no significant difference in mean change between groups.Mean of total cholesterol, TG, LDLc, HDLc concentration and HDLc/LDLc. According to these findings, No significant differences was seen in mean changes of TG, total cholesterol, LDLc, HDLc concentration and HDLc/LDLc between groups. There was no significant difference in TG and total cholesterol before and after the intervention in groups, but LDLc and HDLc/LDLc ratio were significantly increased and HDLc was significantly decreased in OG. Insulin and IR had significant increase and IS had significant decrease in both groups, but β-cell function was significantly increased in OG.Conclusion: Our study showed that no beneficial effects of 2 g/day omega-3 supplement for 6 weeks on biomarkers of Hcy, glucose, insulin and lipid profile in patients with T2D.