We investigated the effect of folic acid supplementation on plasma total homocysteine (tHcy) and carotid intima-media thickness (CIMT) after kidney transplantation. 60 kidney transplantation candidates entered our double blind, randomized, placebo controlled clinical trial. Patients were randomized to receive either 5 mg/day of oral folic acid or equivalent placebo. The main outcome variables were tHcy and CIMT (using B-mode sonography) at baseline and after 2, 4 and 6 months post kidney transplantation. We used independent and paired sample t-test for data analysis. The mean age of the patients was 40.9 ± 10 years and 32 (58.2%) of patients were male. In the control group, the tHcy level at baseline was 19 which reached to 18.7, 19.3 and 20 after 2, 4 and 6 months. At the same times the CIMT measures were 0.81, 0.82, 0.84 and 0.85. The measures were significantly higher than baseline after 4 and 6 months. in the folic acid group the tHcy level at baseline was 18.5 and reached to 14.7, 12.9 and 10.9 after 2, 4 and 6 months. They were significantly lower than baseline at any time after transplantation. At the same times the CIMT measures were 0.73, 0.73, 0.72 and 0.71 which were significantly lower than baseline after 4 and 6 months. tHcy and CIMT were significantly lower in folic acid group after 2 and 4 months, respectively, and continued to be lower thereafter. In conclusion, Folic acid supplementation reduces both tHcy and CIMT shortly after kidney transplantation.