This large dose-ranging study explored the benefits of different combinations of mirabegron and solifenacin on health-related quality of life (HRQoL), based on patient-reported outcomes (PROs), and patients ('responders') achieving clinically meaningful improvements in efficacy and HRQoL. SYMPHONY (NCT01340027) was a Phase II, placebo- and monotherapy-controlled, dose-ranging, 12-week trial. Adult patients with overactive bladder (OAB) for ae3 months were randomized to 1 of 12 groups: 6 combination (solifenacin 2.5/5/10 mg + mirabegron 25/50 mg), 5 monotherapy (solifenacin 2.5/5/10 mg, or mirabegron 25/50 mg), or placebo. Change from baseline to end of treatment was assessed, versus placebo and solifenacin 5 mg in: PROs (OAB-q [Symptom Bother/total HRQoL] and Patient Perception of Bladder Condition score), and responders achieving minimally important differences (MIDs) in PROs and predetermined clinically meaningful improvements in efficacy (e.g. < 8 micturitions/24 h). Changes in PROs and responders were analysed using an ANCOVA model and logistic regression, respectively. The Full Analysis Set included 1278 patients. Combination therapy of solifenacin 5/10 mg + mirabegron 25/50 mg significantly improved PROs versus solifenacin 5 mg and placebo, and significantly more responders achieved MIDs in PROs and efficacy. Micturition frequency normalization was approximately twofold greater with 10 + 25 mg (OR 2.06 [95 % CI 1.11, 3.84; p = 0.023]) and 5 + 50 mg (OR 1.91 [95 % CI 1.14, 3.21; p = 0.015]) versus solifenacin 5 mg. Combining mirabegron 25/50 mg and solifenacin 5/10 mg improves objective and subjective efficacy outcomes compared with placebo or solifenacin 5 mg.