OBJECTIVES Uncontrolled NDO may lead to medical sequelae, such as upper urinary tract complications and renal failure. Treatment choices include BSC (comprised of behavioural therapy and pads, alone or in combination with clean intermittent catheterisation, and possibly with anticholinergics), onabotulinumtoxinA, and surgery. The study’s objective was to determine the cost-effectiveness of onabotulinumtoxinA 200 U vs. BSC among patients inadequately managed with anticholinergics in a UK setting. METHODS A Markov model was developed to compare onabotulinumtoxinA + BSC to BSC alone, with surgery as a downstream option. Efficacy and safety inputs were based on Phase 3 trials. Utility values were derived from a UK preference elicitation study. Costs were obtained from various NHS sources. Model uncertainty was examined through deterministic and probabilistic sensitivity analyses. RESULTS The base case incremental cost-effectiveness ratio (ICER) was £3,856, with an incremental cost of £1,692 and incremental benefits of 0.4387 quality-adjusted life-years (QALYs) for onabotulinumtoxinA + BSC compared with BSC alone over  5 years. A lifetime horizon yielded an ICER of £2,739 per QALY. Univariate sensitivity analyses indicated that the main cost drivers are mean monthly use of catheters and treatment administration costs. Probabilistic sensitivity analysis suggested there would be 100% probability of the ICER being ≤ £10,000. CONCLUSIONS Our analysis suggests that onabotulinumtoxinA + BSC is a cost-effective treatment option, compared with BSC alone for patients with NDO who are inadequately managed with anticholinergics in the UK.