Background: Varicocele is one of the leading causes of infertility in men. Resistance index (RI) in testis is a parameter indicating parenchymal perfusion and microvascular functions. Increased RI in the testis of patients with varicocele might be a sign of impairments in microvascularization and a significant decrease in testicular perfusion. In the present study, RI in capsular and intraparenchymal testicular arteries was evaluated in patients with varicocele who underwent varicocelectomy. Methods: This prospective cohort study was performed in 2019-2020 in Guilan, Iran. Sixty-six patients were included. Semen analysis was also done before surgeries. Patients with at least one disorder in semen analysis entered the study. RI in testicular arteries was measured by an experienced radiologist before surgeries. Six months after varicocelectomy, all patients underwent the same semen analysis and ultrasound imaging. Data were analyzed using SPSS software. The tests for analysis included McNemar Test and Wilcoxon and p<0.005 was considered as the significance level. Results: According to the results, 42 patients (63.6%) had positive changes in sperm analysis after surgeries. Sperm analysis showed a significant increase in number, concentration, morphology, and motility of sperm after surgeries (p<0.001). Further measurements of capsular and intratesticular RI in all patients also indicated a significant decrease (p<0.001). Conclusion: Increased RI might be associated with impaired microperfusion in testis followed by impairments in semen. Moreover, mean capsular and intratesticular RI in patients decreased after surgeries and this decrease was significantly more in patients who had improvement in their semen parameters.