This study quantifies the change in passive ankle range of motion following modified Ponseti casting in children with relapsed idiopathic clubfoot. Fifty-three cases (feet) were retrospectively reviewed, with 6-month follow-up data available for 72% of participants. The median improvement in dorsiflexion was 15° (95% confidence interval: 12.5°-17.5°, P≤0.05), with 85% achieving dorsiflexion≥10°. At the 6-month follow-up, dorsiflexion remained significantly improved and 12 feet (32%) presented with subsequent relapse. Nine were referred for further casting and three were recommended for extra-articular surgery. Repeat modified Ponseti management clinically and statistically improves passive ankle dorsiflexion in relapsed idiopathic clubfoot.