Background: Blunt trauma presents a challenge when external injuries are used to determine or predict the type and severity of internal injuries. Objective: to assess the relationship between internal injuries and external injuries in blunt trauma adult victims. Methodology: This retrospective study was conducted on adult victims of blunt trauma admitted to the Emergency hospital, Tanta University Hospitals from 1st January 2019 to 31st December 2019. Collected variables included sociodemographic data, circumstances of trauma, and sustained injuries. The Abbreviated Injury Scale (AIS) was calculated for external and internal injuries. Results: The study included 311 victims of blunt trauma. A significant association between external and internal injuries was detected in all body regions (p < 0.05), but the positive predictive value (PPV) of external injury was low (below 60%) except for the neck and extremities (75% and 62.4%, respectively). The negative predictive value was ≥90% for all body regions except the head (80.6%). The correlations between AIS of external and internal injuries were positive, moderate, and significant in the neck (rs=0.668, p < 0.001), extremities (rs=0.535, p < 0.001), and head (rs=0.334, p < 0.001), but weak in the chest (rs=0.147, p=0.009) and abdomen (rs=0.123, p=0.030). Conclusion: external injuries are considered as poor indicators of the presence of internal injuries in most body regions. Physicians should not be tempted to rule in or out the presence of internal injury based on external examination. Forensic experts should determine the extent of internal injuries based either on complete autopsy or implement the techniques of the virtual autopsy to avoid misdiagnosing significant internal injuries