Objective: This study aimed to evaluate the effects of transdermal testosterone administration on lower urinary tract symptoms (LUTS) and erectile dysfunction (ED). Materials and Method: Sixty-two male patients with Ageing Male Symptom Questionnaire (AMS-Q) scores over 27 and a total serum testosterone level below 350 ng/dl (12.1 nmol/l) who presented to our urology clinic with complaints of LUTS and ED, were enrolled in this study. Uroflowmetry and the International Prostate Symptom Scale were used to evaluate the severity of LUTS. The International Index of Erectile Function was used to detect the severity of ED. In addition, the AMS-Q was used to quantify the severity of hypogonadism. We randomly divided patients into 2 groups. Thirty-one patients in the first group had transdermal testosterone administered at a daily dose of 50 mg (a sachet of 5 g) on the skin for 3 months. In the second group, 31 patients had a placebo administered for 3 months. The scales were recompleted based on interviews and uroflowmetry was repeated during checks of the patients performed in the first and third months. Results: We detected a decrease in AMS-Q scores and an increase in maximum uroflow rate values and the International Index of Erectile Function scores in the first group compared with the placebo group. Although a decrease was detected in post-treatment International Prostate Symptom Scale scores in the first group, it was not regarded as statistically significant. Conclusion: This study revealed that testosterone replacement therapy is effective in improving LUTS and ED symptoms.