INTRODUCTION: Treatment satisfaction of men receiving phosphodiesterase 5 inhibitors (PDE5) for erectile dysfunction (ED) and their partners is essential to successful long-term therapy. AIM: This study aims to assess treatment satisfaction, in men with a partial response to on-demand (PRN) PDE5 and their female partners, following tadalafil 5 mg once daily or placebo. METHODS: The study was randomized, double-blind, parallel, and placebo-controlled in men primarily with mild to moderate ED. Treatment satisfaction was assessed following a 4-week maximum dose PRN lead-in, 4-week nondrug washout, and treatment through 12 weeks. Men were ≥18 years old with ED for ≥3 months and International Index of Erectile Function Erectile Function score of ≥17 and <26 at screening and <26 following PRN lead-in. MAIN OUTCOME MEASURES: Treatment satisfaction was assessed using the Treatment Satisfaction Scale (TSS) for patients and partners. TSS domain scores range from 0 to 100, with higher values indicating greater satisfaction. Statistical comparisons were made using analysis of covariance. RESULTS: Treatment satisfaction was significantly greater with tadalafil once daily vs. placebo across all TSS domains for both patients and their partners (all P < 0.001). For patients, mean scores for the TSS domains Confidence to Complete Sexual Activity and Satisfaction with Orgasm ranged from 53.7 to 57.8 after the PRN lead-in and 26.7 to 31.9 following the nondrug washout. Following randomized treatment, scores for tadalafil and placebo were 55.4 and 32.6, respectively, for Confidence to Complete Sexual Activity and 57.5 and 37.9, respectively, for Satisfaction with Orgasm. Results were comparable for other TSS domains and between men and their partners. CONCLUSIONS: Treatment satisfaction was comparable for tadalafil 5 mg once daily and PRN PDE5 for both patients and female partners, suggesting that tadalafil once daily is a viable therapy option for men with ED who had a partial response to PRN PDE5 therapy.