Background: Overactive bladder (OAB), a clinical condition with chronic, complex symptoms that negatively affect quality of life (QoL) and affects a large section of the population. Beta-3 adrenergic agonists that provides a different mode of action and are still in the early stages of development, are being used more frequently than antimuscarinics to treat OAB.Aim: To compare between antimuscarinics and a beta-adrenergic agonist (mirabegron) regarding efficacy and side effects in treatment of adult female with overactive bladder. Patients and methods: This prospective trial was carried out in the Obstetrics and Gynecology Department, Faculty of Medicine, Zagazig University on 82 female patients with OAB. Patient groups were divided into two groups (mirabegron 50 mg n = 41 and tolterodine 4 mg n = 41). Results: There was a significant difference between each group's baseline and final assessment in terms of post-void residual urine, number of micturitions, urgency episodes, incontinence episodes, and urgency incontinence episodes/24 h, volume voided/micturition, number of nocturia episodes, and number of incontinences. The only significant difference between the two groups was a lower number of nocturia episodes in mirabegron than tolterodine. Conclusion: In the Egyptian population, with a low incidence of side effects, mirabegron 50 mg and tolterodine 4 mg are efficient therapies for OAB symptoms.