PURPOSE: The efficacy of varicocelectomy in treating infertility among men with ultrasonography-detected subclinical varicocele continues to be a topic of clinical uncertainty. This multicentric, prospective, non-randomized study aimed to evaluate the effect of microsurgical ligation of the internal spermatic vein in men with left subclinical varicocele and no other infertility causes. PATIENTS AND METHODS: The study included 34 infertile men diagnosed with subclinical left varicocele by color Doppler ultrasonography. After a shared decision-making process, the participants self-selected either microsurgical ligation (n = 18) or conservative management (n = 16). Baseline age, duration of infertility, reproductive hormone levels, and semen parameters were comparable across groups. The primary outcomes included changes in sperm concentration, progressive motility, and morphology over a nine-month follow-up period. RESULTS: After nine months, there were no statistically significant differences between the surgery and observation groups in sperm concentration or progressive motility. After adjusting for baseline values, sperm concentration increased by 3 × 10 CONCLUSION: Although this study's small sample size limits its broader generalizability, its findings provide limited evidence that microsurgical ligation may modestly improve sperm morphology in men with subclinical varicocele. Further research with larger, randomized cohorts is warranted to confirm these results and assess potential fertility outcomes.