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 and laparoscopic Palomo surgery in a tertiary referral center. Patients with left grade 3 varicocele indicated for surgery were prospectively enrolled and randomly allocated to the scrotal antegrade sclerotherapy and laparoscopic Palomo surgery groups, with their respective contralateral normal testes taken as controls. The primary outcome measures were clinical varicocele recurrence, testicular catch-up growth, and postoperative 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 (scrotal antegrade sclerotherapy, n = 57; laparoscopic Palomo surgery, n = 56). All patients had significantly smaller testes preoperatively; the testicular volume differences with control testes were -23% in scrotal antegrade sclerotherapy and -19% in laparoscopic Palomo surgery. At 12-month follow-up, there were no statistically significant differences in clinical recurrences between the 2 groups (scrotal antegrade sclerotherapy = 5.3% vs laparoscopic Palomo surgery = 5.4%, > .05, noninferiority test). Testicular catch-up growths were observed in both groups; the mean testicular volume difference between the treatment and control testes decreased from -23% to -8.1% in scrotal antegrade sclerotherapy ( < .001) and from -19% to -9.3% in laparoscopic Palomo surgery ( < .001) at 12-month follow-up. There was no postoperative hydrocele in the scrotal antegrade sclerotherapy group compared to 7 cases in the laparoscopic Palomo surgery group (0% vs 13%, = .006). Both scrotal antegrade sclerotherapy and laparoscopic Palomo surgery are safe and effective procedures for treatment of adolescent varicocele with significant positive effect on testicular catch-up growth. Scrotal antegrade sclerotherapy is not inferior to laparoscopic Palomo surgery in terms of clinical recurrence rate and has significantly less postoperative hydrocele.