Objective. To evaluate an efficacy and safety of rehabilitation in intensive care unit (ICU) depending on the time of rehabilitation onset. Material and methods. The study included data of 148 patients (106 patients with sepsis and postoperative complications and 42 patients with acute brain impairment) who received daily rehabilitation treatment for at least 7 days at the ICU for the period from 2017 to 2019. All patients were retrospectively assigned to the group of early rehabilitation (ER), if rehabilitation treatment was started within 48 hours after admission to ICU. The group of delayed rehabilitation (DR) included instable patients and those with impossible early mobilization. Results. Baseline clinical and demographic characteristics were similar in both groups. Incidence of infectious complications and vasopressor support was also comparable throughout rehabilitation. Duration of mechanical ventilation in patients without acute brain impairment was 8 (6) days in the ER group and 13 (9) days in the DR group (p=0.003). ICU-stay in the same catego-ry of patients was longer in the DR group compared to the ER group (19 (13—30) and 12 (9—16) days, respectively; p