Varicocele is a common condition in adolescence and the most common correctable cause of infertility. This study aimed to analyze and compare the outcomes of scrotal antegrade sclerotherapy (SAS) and laparoscopic Palomo surgery (LPS) in a tertiary referral centre. Patients with left grade 3 varicocele indicated for surgery were prospectively enrolled and randomly allocated to the SAS and LPS groups, with their respective contralateral normal testes taken as controls. The primary outcome measures were clinical varicocele recurrence, testicular catch-up growth, and post-operative hydrocele. All patients were evaluated clinically and using Doppler ultrasound by radiologists. From 2015 to 2020, 113 patients completed the study and were statistically analyzed (SAS, n = 57; LPS, n = 56). All patients had significantly smaller testes pre-operatively that the testicular volume differences with control testes were -23% in SAS and -19% in LPS. At 12-month follow-up, there were no statistical significant difference in clinical recurrences between the 2 groups (SAS = 5.3% vs LPS = 5.4%, P>.05, non-inferiority test). Testicular catch-up growths were observed in both groups, the mean testicular volume difference between the treatment and control testes reduced from -23% to -8.1% in SAS (P<.001) and -19% to -9.3% in LPS (P<.001) at 12-month follow-up. There was no post-operative hydrocele in SAS compared to 7 in LPS (0% vs 13%, P = .006). Both SAS and LPS are safe and effective procedures for treatment of adolescent varicocele with significant positive effect on testicular catch-up growth. SAS is not inferior to LPS in terms of clinical recurrence rate and with significantly less post-operative hydrocele.