Background and Objectives: Thoracic trauma usually results in high morbidity and mortality. It is the leading cause of death in patients within the first four decades of life. In this study, we aimed to identify risk factors for intensive care mortality and to evaluate factors affecting clinical outcomes and complications in patients with thoracic trauma who were treated in the intensive care unit (ICU). Materials and Methods: This was a retrospective, single-center study. Patients diagnosed with thoracic trauma and followed up in the ICU between 1 May 2023 and 1 January 2025 were included. Critically ill patients aged 18 years and older whose admission blood values were available and who had undergone radiological imaging were included in the study. Patients were grouped as Survivors or Non-survivors. The primary outcome was to determine risk factors for mortality. The secondary outcome was to evaluate factors affecting clinical outcomes and complications. The tertiary outcome was to determine the predictive value of the Injury Severity Score (ISS), Acute Physiology and Chronic Health Evaluation II (APACHE II), and Glasgow Coma Scale (GCS) for mortality. Results: A total of 104 patients (male/female ratio: 76/28) were included in the study. Twenty-four patients (23.1%) died, and eighty (76.9%) were discharged. Age in the Non-survivor group was found to be significantly higher (59.33 ± 22.21 vs. 40.50 ± 17.71; p < 0.001), and the proportion of women was also significantly higher in the Non-survivor group (p = 0.0082). Mortality was associated with advanced age, female sex, lower GCS score (p < 0.001), higher APACHE II scores (p < 0.001), and the presence of comorbid conditions (p = 0.003), including head trauma (p = 0.024) and cardiac arrest before ICU admission (p = 0.011). The Non-survivor group more frequently required mechanical ventilation (p < 0.001), vasopressor support (p < 0.001), and continuous renal replacement therapy (p < 0.001), and they developed ventilator-associated pneumonia (p < 0.001) and acute respiratory distress syndrome (p < 0.001) at higher rates. ICU length of stay was also significantly longer in the Non-survivor group (p = 0.045). The APACHE II score demonstrated the highest discriminatory performance, emerging as the strongest clinical predictor of mortality (AUC = 0.751, 95% CI: 0.630–0.872; p < 0.001). Age (OR: 1.06) and serum lactate levels (OR: 1.57) consistently emerged as strong independent predictors of mortality. The presence of head trauma significantly increased the risk of mortality, particularly in the APACHE II-adjusted model (OR: 9.08). The APACHE II–based model yielded high specificity (96.3%) and accuracy (88.5%), with good discrimination (AUC = 0.894) and the highest Nagelkerke R2 (0.548). Conclusions: Factors that may shorten the length of ICU stay include infection control, early correction of acidosis, and maintenance of hemodynamic stability, which may reduce mortality. APACHE II was more closely related to overall clinical severity than the other scoring systems. Our data indicate that age-related frailty and acute physiological derangement, as best represented by the APACHE II score, are more significant determinants of survival than anatomic injury severity alone.