Purpose: The objective of this manuscript is to assess the effect of varicocele repair (VR) in patients with clinical varicoceles on serum total testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and inhibin B serum levels. Materials and Methods: The study was performed in compliance with the Meta-Analysis and Systematic Reviews of Observational Studies (MOOSE) guidelines and the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P). All eligible studies were selected following the PICOS (Population, Intervention, Comparison/Comparator, Outcomes, Study design) model. The values of each outcome measured after VR were compared to the before parameters and, when available, to the values on patients with unrepaired varicocele, and to those of healthy controls with no varicocele. For total testosterone, the values were sub-analyzed based on the mean total testosterone levels before VR (<300 ng/dL or >300 ng/dL), the fertility status, the time of follow-up and the technique used for VR. Results: From a total of 460 abstracts retrieved, 48 articles were included in our meta-analysis. Serum total testosterone levels were significantly higher after VR compared to both pre-treatment levels (mean difference [MD] 82.45 ng/dL, 95% confidence interval [CI]: 64.14-100.76; p<0.00001) and to the levels of patients with unrepaired varicocele (MD 91.64 ng/dL, 95% CI: 62.30-120.99; p<0.00001). They did not differ from the levels of healthy controls with no varicocele (MD -22.01 ng/dL, 95% CI: -68.59-24.58; p=0.35). The increase resulted to be independent from the mean total testosterone levels before VR, fertility status, time of follow-up and type of VR. After VR, a trend toward lower serum LH levels was found compared to before values (MD -0.37 IU/L, 95% CI: -0.74-0.01; p=0.06). When compared to the levels of patients with unrepaired VR, LH levels after VR were significantly lower (MD -0.96 IU/L, 95% CI: -1.56 to -0.35; p=0.002). LH levels were not significantly higher than healthy men without varicocele (MD 0.84 IU/L, 95% CI: -0.68-2.36; p=0.28). Patients with VR had significantly lower FSH levels compared to their pre-treatment values (MD -1.43 IU/L, 95% CI: -1.82 to -1.04; p<0.00001), and also to those of patients with non-repaired varicocele (MD -2.35 IU/L, 95% CI: -4.06 to -0.65; p=0.007). When compared to healthy controls with no varicocele, FSH levels were significantly higher (MD 2.71 IU/L, 95% CI: 1.12-4.31; p=0.0009). Lastly, after VR no significant change in inhibin B serum levels was seen compared to pre-treatment levels (MD 11.76 pg/mL, 95% CI: -3.83-27.35; p=0.14). Conclusions: The present meta-analysis is the largest to date to assess the impact of VR on Leydig cell and Sertoli cell function using a before-after analysis for uncontrolled studies, and using data from patients with unrepaired varicoceles or healthy patients without varicocele as controls. VR was found to increase and restore to normality serum levels of total testosterone and LH. This evidence could be of value in considering the treatment of varicocele in patients with low testosterone or those who show a progressive decline in testosterone levels.