Abstract Introduction: The negative impact of prolonged immobilization results a physical decline during hospitalization in patients with acute brain injury. Objective: To investigate the benefits of early exercises on the mobility of patients with acute brain injury assisted at an Intensive Care Unit (ICU). Methods: This is a prospective, single-blind, controlled clinical trial. A total of 303 patients were assessed. Due to eligibility criteria, exercise protocol was applied in 58 participants, 32 with brain injury caused by traumatic event and 26 with brain injury caused by cerebrovascular event. Exercise began 24 hours after patients’ admission at the ICU. Participants were submitted to passive and active mobilization protocols, performed according to level of sedation, consciousness and collaboration. Statistical analysis was conducted with repeated measures analysis of variance. Significance was set at 5%. Results: The group of patients with traumatic brain injuries was younger (p = 0.001) and with more men (p = 0.025) than the group of patients with clinical events. Most exercise sessions were performed in sedated patients. By the end of the protocol, participants with traumatic and clinical brain injury were able to do sitting and standing exercises. Both groups were similar on ICU discharge (p = 0.290). The clinical group presented better improvement on level of consciousness than the traumatic group (p = 0.005). Conclusion: Participants with an acute brain injury presented at the time of discharge from the ICU good mobility and improvement in the level of consciousness.