PURPOSE: Sacral neuromodulation and intradetrusor onabotulinumtoxinA injection are therapies for refractory urgency urinary incontinence. Sacral neuromodulation involves surgical implantation of a device that can last 4 to 6 years while onabotulinumtoxinA therapy involves serial office injections. We assessed the cost-effectiveness of 2-stage implantation sacral neuromodulation vs 200 units onabotulinumtoxinA for the treatment of urgency urinary incontinence. MATERIALS AND METHODS: Prospective economic evaluation was performed concurrent with the ROSETTA (Refractory Overactive Bladder: Sacral NEuromodulation vs. BoTulinum Toxin Assessment) randomized trial of 386 women with 6 or more urgency urinary incontinence episodes on a 3-day diary. Analysis is from the health care system perspective with primary within-trial analysis for 2 years and secondary 5-year decision analysis. Costs are in 2018 U.S. dollars. Effectiveness was measured in quality adjusted life-years (QALYs) and reductions in urgency urinary incontinence episodes per day. We generated incremental cost-effectiveness ratios and cost-effectiveness acceptability curves. RESULTS: Two-year costs were higher for sacral neuromodulation than for onabotulinumtoxinA ($35,680 [95% CI 33,920-37,440] vs $7,460 [95% CI 5,780-9,150], p <0.01), persisting through 5 years ($36,550 [95% CI 34,787-38,309] vs $12,020 [95% CI 10,330-13,700], p <0.01). At 2 years there were no differences in mean reduction in urgency urinary incontinence episodes per day (-3.00 [95% CI -3.38 - -2.62] vs -3.12 [95% CI -3.48 - -2.76], p=0.66) or QALYs (1.39 [95% CI 1.34-1.44] vs 1.41 [95% CI 1.36-1.45], p=0.60). The probability that sacral neuromodulation is cost-effective relative to onabotulinumtoxinA is less than 0.025 for all willingness to pay values below $580,000 per QALY at 2 years and $204,000 per QALY at 5 years. CONCLUSIONS: Although both treatments were effective, the high cost of sacral neuromodulation is not good value for treating urgency urinary incontinence compared to 200 units onabotulinumtoxinA.