Background: Women with refractory urgency urinary incontinence (ie, unresponsive to behavioral and pharmacological interventions) are treated with onabotulinumtoxinA or sacral neuromodulation. Objective: The objective of the study was to compare treatment efficacy and adverse events in women <65 and ≥65 years old treated with onabotulinumtoxinA or sacral neuromodulation. Study Design: This study was a planned secondary analysis of a multicenter, randomized trial that enrolled community-dwelling women with refractory urgency urinary incontinence to onabotulinumtoxinA or sacral neuromodulation treatments. The primary outcome was a change in mean daily urgency urinary incontinence episodes on a bladder diary over 6 months. Secondary outcomes included ≥75% urgency urinary incontinence episode reduction, change in symptom severity/quality of life, treatment satisfaction, and treatment-related adverse events. Results: Both age groups experienced improvement in mean urgency urinary incontinence episodes per day following each treatment. There was no evidence that mean daily urgency urinary incontinence episode reduction differed between age groups for onabotulinumtoxinA (adjusted coefficient, –0.127, 95% confidence interval, –1.233 to 0.979; P =.821) or sacral neuromodulation (adjusted coefficient, –0.698, 95% confidence interval, –1.832 to 0.437; P =.227). Among those treated with onabotulinumtoxinA, women <65 years had 3.3-fold greater odds of ≥75% resolution than women ≥65 years (95% confidence interval, 1.56 –7.02). Women <65 years had a greater reduction in Overactive Bladder Questionnaire Short Form symptom bother scores compared with women ≥65 years by 7.49 points (95% confidence interval, –3.23 to –11.74), regardless of treatment group. There was no difference between quality of life improvement by age. Women ≥65 years had more urinary tract infections following onabotulinumtoxinA and sacral neuromodulation (odds ratio, 1.9, 95% confidence interval, 1.2–3.3). There was no evidence of age differences in sacral neuromodulation revision/removal or catheterization following onabotulinumtoxinA treatment. Conclusion: Younger women experienced greater absolute continence, symptom improvement, and fewer urinary tract infections; both older and younger women had beneficial urgency urinary incontinence episode reduction, similar rates of other treatment adverse events, and improved quality of life.