Background: Nonlinear analysis of heart rate variability (HRV) has been recently used as a predictor of prognosis in trauma patients. Objectives: We applied nonlinear analysis of HRV in patients with blunt trauma and intraperitoneal bleeding to assess our ability to predict the outcome of conservative management. Patients and Methods: An analysis of electrocardiography (ECG) from 120 patients with blunt trauma was conducted at the onset of admission to the emergency department. ECGs of 65 patients were excluded due to inadequacy of noise-free length. Of the remaining 55 patients, 47 survived (S group) and eight patients died in the hospital (Non-S group). Nineteen patients were found to have intra-abdominal bleeding, eight of which ultimately underwent laparotomy to control bleeding (Op group) and 11 underwent successful non-operative management (non-Op). Demographic data including vital signs, glasgow coma scale (GCS), arterial blood gas and injury severity scores (ISS) were recorded. Heart rate complexity (HRC) methods, including entropy, were used to analyze the ECG. Results: There were no differences in age, gender, heart rate (HR) and blood pressure between the S and Non-S groups. However, approximate entropy, used as a method of HRC measurement, and GCS were significantly higher in S group, compared to the Non-S group. The base deficit and ISS were significantly higher in the Non-S group. Regarding age, sex, ISS, base deficit, vital signs and GCS, no difference was found between Op and Non-Op groups. Approximate entropy was significantly lower in the Op group, compared to the Non-Op group. Conclusions: The loss of HRC at the onset of admission may predict mortality in patients with blunt trauma. Lower entropy, in recently admitted patients with intra-abdominal bleeding, may indicate laparotomy when the vital signs are stable.