OBJECTIVES Mirabegron, a β-adrenoceptor agonist approved for the treatment of overactive bladder (OAB), has been shown to reduce OAB symptoms and improve HRQoL relative to placebo and to cause a lower incidence of dry mouth than tolterodine. We investigated the cost-effectiveness of mirabegron 50mg compared to tolterodine ER 4mg. METHODS A Markov model was developed to simulate management, symptom changes (micturitions, incontinence), and adverse events in OAB patients. The model predicted costs and QALYs over 1 year in a hypothetical cohort of Canadian patients previously treated for OAB. The analysis compared treatment with mirabegron 50mg to tolterodine ER 4mg, administered in a reference arm in the pivotal study SCORPIO and one of the antimuscarinic options most widely prescribed and funded in Canada for the treatment of OAB, from both a payer (Ontario Ministry of Health and Long-term Care [MOH]) and societal perspective. Clinical and health state utility data for the model were based on the previously treated OAB population of SCORPIO. Transition probabilities between symptom severities were obtained using multinomial logistic regression models estimated from SCORPIO. Probabilities of discontinuation and switching therapy were derived from the literature. Resource utilisation estimates were based on clinical trial data, the literature and expert opinion. Unit costs were derived from official schedules for Ontario and published Canadian literature. Deterministic and probabilistic sensitivity analyses were performed. RESULTS Mirabegron 50mg dominated tolterodine ER 4mg: incremental cost savings were CA$118.91 (MOH perspective) and CA$140.48 (societal); and 0.005 QALYs (MoH and societal) were gained. ICERs were robust over a wide range of sensitivity analyses, but were most sensitive to micturition symptom levels for tolterodine and to costs of subsequent therapy. CONCLUSIONS Treatment with mirabegron 50mg is cost-effective compared with tolterodine ER 4mg in a population previously treated for OAB from Canadian healthcare and societal perspectives.