IntroductionVery few studies have examined patterns of physical activity (PA) during a pulmonary rehabilitation (PR) program in people with COPD. AimsTo compare the patterns of PA in: 1) the week before commencing PR (pre-PR) with a week during PR (PR week); 2) PR days and non-PR days during a PR week; 3) pre-PR and the week following PR completion (post-PR). MethodsThis was a multicenter, prospective cohort study. Participants attended twice weekly supervised PR for 8–12 weeks. Daily step count (primary outcome), time in light activities, time in moderate to vigorous PA (MVPA), total sedentary time and sit-to-stand (STS) transitions were measured using a thigh worn accelerometer for seven days, at each assessment time point: pre-PR, PR week and post-PR. Results29 participants, mean age (SD) 69years(7), FEV1 53%pred(16). The PR week compared to pre-PR, showed higher daily: step count (mean difference (95%CI)), 941steps(388–1494); and MVPA, 11mins(6–15), with no difference in: time in light activities, -1min(-6–5); total sedentary time, 7mins(-21–36); or STS transitions, 0(-5–6). PR days compared to non-PR days showed higher: step count, 2810steps(1706–3913); time in light activities 11mins(1–20); time in MVPA, 27mins(17–35) and STS transitions, 8(4–12), with no difference in total sedentary time: −33mins(-80–15). There were no differences in any PA measures post-PR compared to pre-PR (p < 0.05). ConclusionDaily step count and time spent in MVPA increased significantly during the PR week, solely due to increased PA on days participants attended PR.