Background: Point-of-care ultrasound (POCUS), and particularly the Focused Assessment with Sonography in Trauma (FAST), is widely used for the rapid detection of life-threatening internal injuries in trauma settings. In low-resource environments, where access to whole-body computed tomography may be limited, FAST plays a pivotal role in early triage and therapeutic decision-making. This study aimed to assess the diagnostic contribution of FAST in the initial evaluation of polytrauma patients admitted to the Emergency Department of Gabriel Touré University Hospital. Methods: We conducted a prospective, observational, descriptive study over six months (July–December 2022) in the Emergency Department of CHU Gabriel Touré, Mali. All trauma patients presenting with hemodynamic instability (systolic blood pressure ≤ 90 mmHg) were eligible. Non-consenting patients or those who died before undergoing FAST were excluded. Ultrasound examinations were performed using a Siemens Acuson X300 device equipped with cardiac, linear, and convex probes. Clinical, epidemiological, FAST findings, CT scan results, therapeutic interventions, orientation, and outcomes were collected and analyzed using SPSS 26.0, applying chi-square and logistic regression tests (significance threshold p < 0.05). Results: A total of 42 polytrauma patients were included among 9050 trauma admissions (frequency 0.46%). Road traffic accidents predominated (80.95%), with high-energy mechanisms commonly observed: projection (35.71%), crushing (26.19%), and vehicle ejection (23.80%). Chest pain (90.50%) and dyspnea (42.85%) were the most frequent symptoms. FAST was pathological in 64.28% of patients, mainly showing hemoperitoneum (40.48%). Thoracic lesions detected on FAST included pneumothorax (9.52%), hemothorax (4.76%) and hemopneumothorax (9.52%). CT scans confirmed numerous severe injuries, including rib fractures (38.10%), flail chest (26.19%), and abdominal injuries in 78% of cases. Emergency interventions w