BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is characterised by worsening dyspnoea and exercise intolerance. RESEARCH QUESTION: Does a long-term pulmonary rehabilitation improve exercise tolerance in patients with IPF treated with standard antifibrotic drugs, which are expected to reduce disease progression? METHODS: This open-label randomised controlled trial was performed at 19 institutions. Stable patients receiving nintedanib were randomised into pulmonary rehabilitation and control groups (1:1). The pulmonary rehabilitation group underwent initial rehabilitation which included twice-weekly sessions of monitored exercise training for 12 weeks, followed by an at-home rehabilitation programme for 40 weeks. The control group received usual care only, without pulmonary rehabilitation. Both groups continued to receive nintedanib. The primary and main secondary outcomes were change in 6 min walking distance (6MWD) and change in endurance time (using cycle ergometry) at week 52. RESULTS: Eighty-eight patients were randomised into pulmonary rehabilitation (n=45) and control (n=43) groups. Changes in 6MWD were -33 m (95% CI -65 to -1) and -53 m (95% CI -86 to -21) in the pulmonary rehabilitation and control groups, respectively, with no statistically significant difference (mean difference, 21 m (95% CI -25 to 66), p=0.38). Changes in endurance time were significantly better in the pulmonary rehabilitation (64 s, 95% CI -42.3 to 171)) than in the control (-123 s (95% CI -232 to -13)) group (mean difference, 187 s (95% CI 34 to 153), p=0.019). INTERPRETATION: Although pulmonary rehabilitation in patients taking nintedanib did not improve 6MWD in the long term, it led to prolonged improvement in endurance time. TRIAL REGISTRATION NUMBER: UMIN000026376.