Background Electrocardiographic (ECG) changes occurring during the course of acute brain injury (ABI) have been described frequently, but their significances remain uncertain. The present study was designed to investigate the relation of ECG abnormalities to outcome in the patients with ABI. Methods We performed a retrospective, observational study on the ABI patients admitted to the Department of Neurosurgery of the Beijing Tiantan Hospital between December 2005 and December 2007. All the patients accepted 12-lead electrocardiographic examination within 24 hours after injury, then divided into three groups according to the Glasgow coma score (GCS). In-hospital mortality and one-month outcome assessed by the Glasgow outcome score (GOS) were investigated. Results Of 335 ABI patients (mean ages 32.4 years), 246 patients (73.4%) had abnormal ECGs. The most common abnormality was ST-T changes (41.5%), followed by sinus tachycardia (23.6%). ECG changes had a significant association with the severity and outcome. Logistic regression analysis showed the presence of ST-T changes (OR 2.587, 95%C/1.009 to 6.629, P=0.048) and QT dispersion prolongation (OR 4.656, 95%C/1.956 to 11.082, P=0.001) significantly associated with short outcomes. Conclusions ABI can lead to myocardial damage and ECG changes had a significant association with the severity. ST-T changes and QT dispersion prolongation were the independent prognosis factors for the negative outcome of ABI patients.