OBJECTIVES: Mirabegron, a novel selective beta-3 adrenergic agonist, has recently been approved in the United States for the treatment of overactive bladder (OAB). This study aimed to assess the impact of mirabegron on Work Productivity and Activity Impairment (WPAI) and the associations between WPAI outcomes and OAB symptom severity.  METHODS: Data were obtained from a 12-week phase III randomized trial (NCT00662909) comparing mirabegron 50mg and placebo for OAB treatment. WPAI outcomes were measured using the WPAI-Questionnaire for OAB, including employment and total activity impairment (TAI) for all patients, and absenteeism, presenteeism and total work productivity impairment (TWPI) for employed patients. OAB severity measures included number of incontinence and micturition episodes/day. Analyses of covariance were used to assess the effects of mirabegron on baseline-week 12 changes in WPAI. Longitudinal generalized estimating equations and Pearson correlation coefficients were used to assess associations between WPAI and OAB severity. Subgroup analyses were conducted for patients who discontinued prior OAB medication due to insufficient efficacy. RESULTS: Among the study sample (total N=858, employed N=394), mirabegron-treated patients experienced significantly greater improvement in TAI (12.3% vs. 6.7%, p<0.01) and greater but non-significant improvements in absenteeism (0.2% vs. -0.5%), presenteeism (8.6% vs. 6.0%), and TWPI (8.2% vs. 5.8%) than placebo-treated patients at week 12. . Based on the association analyses, 2.0%, 1.4% and 1.4% increases per additional incontinence episode and, 1.2%, 1.1% and 1.1% increases per additional micturition episode were observed in  TAI, presenteeism, and TWPI respectively (p<0.01). Baseline-week 12 change in TAI was significantly correlated with changes in OAB severity (incontinence: r=0.17, micturition: r=0.11; p<0.01). Similar trends were observed in the patient-subgroup with prior treatment non-response.  CONCLUSIONS: Patients treated with mirabegron experience significantly reduced total activity impairment. Impairments in work productivity and activity outcomes are associated with OAB symptom severity, suggesting that treatments that improve symptom severity may also improve productivity impairment.