INTRODUCTION: Tadalafil improves lower urinary tract symptoms (LUTS) including nocturia. However, the effect of tadalafil on the nocturia-related quality of life (QoL) is still unknown. OBJECTIVE: The effects of tadalafil on nocturia and nocturia-related QoL were evaluated prospectively in patients with benign prostatic hyperplasia (BPH) as a multicenter study. METHODS: Eligible men were ≥40 years with nocturia ≥2 and a prostate volume ≥20 mL. Patients were asked to complete a self-report questionnaire on the International Prostate Symptom Score (IPSS), the Nocturia Quality of Life questionnaire (N-QoL) and the International Index of Erectile Function 5 (IIEF5). Urinary frequency volume charts (FVCs) were also evaluated. These measures were evaluated at baseline, and after 4, 8, and 12 weeks of tadalafil administration (5 mg once daily). RESULTS: Thirty-one patients with a mean age of 74 years, a mean prostate volume of 31 mL, and a mean prostate-specific antigen level of 2.8 ng/mL were included. Treatment with tadalafil significantly improved their nocturia after 4 weeks, and these improvements were maintained for the 12-week treatment period. Total N-QoL score in new patients and several N-QoL items (inadequate sleep at night and overall bother) in all patients improved significantly after tadalafil treatment. FVCs revealed a significant improvement in the number of hours of undisturbed sleep (HUS) after treatment with tadalafil. No serious adverse events were observed. CONCLUSIONS: This study indicates that tadalafil 5 mg once daily improves nocturia, nocturia-related QoL, and HUS in BPH patients with nocturia. These results suggest that tadalafil can offer a clinically meaningful treatment option for BPH patients with nocturia.