Background: Readmission to the Intensive Care Unit (ICU) is a significant adverse event associated with increased mortality, prolonged hospital length of stay (LOS), and higher healthcare costs. While general ICU readmission rates and predictors are well-studied, the specific context of a Level I Trauma Center ICU—characterized by a unique, acutely injured, and heterogeneous patient population—requires focused analysis. Objective: This study aims to determine the incidence, timing, primary causes, and independent risk factors associated with ICU readmission within the same hospitalization for patients in a Level I Trauma Center ICU, and to evaluate its impact on patient outcomes. Methods: A retrospective cohort study was conducted over a three-year period at the Level I Trauma Center of a major academic hospital. All adult patients (≥18 years) admitted to the trauma ICU (TICU) were included. Data were extracted from the institutional trauma registry and electronic health records. Patients who were readmitted to the TICU (case group) were compared with those who had a single, continuous TICU stay (control group). Analyzed variables included demographics, injury characteristics (ISS, AIS, mechanism), pre-existing comorbidities, physiological and laboratory data at initial ICU discharge, processes of care (timing of discharge, nurse-to-patient ratio), and outcomes (mortality, total LOS, ICU LOS). Multivariable logistic regression was used to identify independent predictors of ICU readmission. Results: Of 4,217 initial TICU admissions, 178 (4.2%) required readmission. The median time to readmission was 3 days (IQR: 2-5 days). The leading causes for readmission were respiratory failure (32.6%), neurological deterioration (24.7%), and sepsis/septic shock (18.5%). Independent risk factors for readmission included: higher Injury Severity Score (ISS) (OR 1.03 per point, 95% CI 1.01-1.05), severe traumatic brain injury (AIS head ≥3) (OR 2.1, 95% CI 1.5-3.0), pre-existing chronic obstructive pulmonary disease (COPD) (OR 2.3, 95% CI 1.4-3.7), and discharge from the ICU during night shifts (20:00-08:00) (OR 1.8, 95% CI 1.2-2.7). Patients with ICU readmission had significantly higher in-hospital mortality (15.2% vs. 6.1%, p<0.001), longer median total hospital LOS (28 vs. 14 days, p<0.001), and longer cumulative ICU LOS (12 vs. 5 days, p<0.001). Conclusion: ICU readmission in a Level I Trauma Center is a relatively frequent occurrence associated with markedly worse outcomes. It is strongly linked to injury severity, specific injury patterns (TBI), underlying comorbidities (COPD), and potentially modifiable system factors like night-time discharge. These findings highlight the need for tailored discharge planning, enhanced monitoring of high-risk patients, and protocolized weaning and handover processes to mitigate this critical quality metric.