BackgroundThe level of post‐operative mobilization according to Enhanced Recovery After Surgery (ERAS) guidelines is not always achieved. We investigated whether immediate mobilization increases postoperative physical activity. The objective was to evaluate the effects of immediate postoperative mobilization in the post‐anesthesia care unit (PACU) compared to standard care.MethodsThis randomized controlled trial, involved 144 patients, age ≥18 years, undergoing elective colorectal surgery. Patients were randomized to mobilization starting 30 min after arrival in the PACU, or to standard care. Standard care consisted of mobilization a few hours later at the ward according to ERAS guidelines. The primary outcome was physical activity, in terms of number of steps, measured with an accelerometer during postoperative days (PODs) 1–3. Secondary outcomes were physical capacity, functional mobility, time to readiness for discharge, complications, compliance with the ERAS protocol, and physical activity 1 month after surgery.ResultsWith the intention‐to‐treat analysis of 144 participants (median age 71, 58% female) 47% underwent laparoscopic‐or robotic‐assisted surgery. No differences in physical activity during hospital stay were found between the participants in the intervention group compared to the standard care group (adjusted mean ratio 0.97 on POD 1 [95% CI, 0.75–1.27], p = 0.84; 0.89 on POD 2 [95% CI, 0.68–1.16], p = 0.39, and 0.90 on POD 3 [95% CI, 0.69–1.17], p = 0.44); no differences were found in any of the other outcome measures.ConclusionsAddition of the intervention of immediate mobilization to standard care did not make the patients more physically active during their hospital stay.Trial registrationClinicalTrials.gov Identifier: NTC 03357497.