We investigated the effects of Antep pistachio on International Index of Erectile Function (IIEF) scores, penile color Doppler ultrasound (PCDU) parameters and serum lipid levels in patients with ED. A total of 17 married male patients with ED for at least 12 months were included in this prospective study. Patients were put on a 100 g pistachio nuts diet for 3 weeks. IIEF and PCDU were evaluated before and after the pistachio diet. In addition, plasma total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglyceride were measured before and after dietary modifications from all subjects. Mean IIEF-15 score was 36 ± 7.5 before the diet and 54.2 ± 4.9 after the diet (P=0.001). Similarly, an increase in all five domains of IIEF was observed after the diet (P<0.05). Mean peak systolic velocity values before and after the pistachio diet were 35.5 ± 15.2 and 43.3 ± 12.4 cm s(-1), respectively (P=0.018). After the pistachio diet, TC and LDL levels decreased significantly, whereas HDL level increased (P=0.008, 0.007 and 0.001, respectively). We demonstrated that a pistachio diet improved IIEF scores and PCDU parameters without any associated side effects in patients with ED. Furthermore, the lipid parameters showed statistically significant improvements after this diet.