How cost-effective is group-based pelvic floor muscle training (PFMT) for treating urinary incontinence in older women? Economic evaluation conducted alongside an assessor-blinded, multicentre randomised non-inferiority trial with 1-year follow-up. A total of 362 women aged ≥ 60 years with stress or mixed urinary incontinence. Twelve weekly 1-hour PFMT sessions delivered individually (one physiotherapist per woman) or in groups (one physiotherapist per eight women). Urinary incontinence-related costs per woman were estimated from a participant and provider perspective over 1 year in Canadian dollars, 2019. Effectiveness was based on reduction in leakage episodes and quality-adjusted life years. Incremental cost-effectiveness ratios and net monetary benefit were calculated for each of the effectiveness outcomes and perspectives. Both group-based and individual PFMT were effective in reducing leakage and promoting gains in quality-adjusted life years. Furthermore, group-based PFMT was ≥ 60% less costly than individual treatment, regardless of the perspective studied: -$914 (95% CI -970 to -863) from the participant's perspective and -$509 (95% CI -523 to -496) from the provider's perspective. Differences in effects between study arms were minor and negligible. Adherence to treatment was high, with low loss to follow-up and no between-group differences. Compared with standard individual PFMT, group-based PFMT was less costly and as clinically effective and widely accepted. These results indicate that patients and healthcare decision-makers should consider group-based PFMT to be a cost-effective first-line treatment option for urinary incontinence. ClinicalTrials.govNCT02039830.