<b><i>Introduction:</i></b> Randomized controlled trials (RCTs) of testosterone therapy (TTh) for late-onset hypogonadism are systematically reviewed and a meta-analysis to assess the efficacy of TTh in improving erectile function is performed. <b><i>Methods:</i></b> The PubMed, Cochrane Library, and Web of Science databases were searched to identify RCTs published from 2007. RCTs that assessed erectile function using the erectile function domain of the International Index of Erectile Function (IIEF-EFD) were included in the meta-analysis. <b><i>Results:</i></b> The systematic review included 18 RCTs and the meta-analysis included 6 studies that enrolled a total of 1,458 patients. The overall meta-analysis revealed that the IIEF-EFD score was significantly improved in the TTh group compared with the placebo group (mean difference 1.86; 95% confidence interval 1.01–2.72; <i>p</i> &#x3c; 0.0001). Compared with patients receiving placebo, there was a significant improvement in the IIEF-EFD of patients who received TTh using testosterone gel, those who received TTh for over 30 weeks, and those without diabetes mellitus or metabolic syndrome. <b><i>Conclusion:</i></b> TTh achieved a significant improvement in the IIEF-EFD score of hypogonadal men compared with placebo, especially in those who received testosterone gel, were treated for over 30 weeks, and had no comorbidities.