Purpose <p>Sternal fractures (SF) are relatively uncommon but clinically important injuries, frequently accompanied by rib fractures, pulmonary complications, and the need for intensive care unit (ICU). Despite advances in imaging and trauma management, prognostic assessment in SF remains challenging. In particular, the comparative performance of commonly used trauma severity scores—Injury Severity Score (ISS), New Injury Severity Score (NISS), and Trauma and Injury Severity Score (TRISS)—has not been clearly established in this patient group.</p> Methods <p>This retrospective observational study included 393 adult patients diagnosed with SF at a tertiary trauma center. The prognostic performance of ISS, NISS, and TRISS for ICU admission was evaluated using ROC analysis, pairwise ROC comparison, multivariable logistic regression, and exploratory decision-tree modeling.</p> Results <p>In-vehicle traffic accidents were the most common mechanism of injury (60.1%). Most patients were managed conservatively (95.7%), with an overall mortality rate of 3.1%. ROC analysis showed good discriminatory ability for ICU admission with NISS (AUC [Area Under the Curve] 0.876) and ISS (AUC 0.847), whereas TRISS performed moderately (AUC 0.743). In multivariable models, ISS and NISS remained independently associated with ICU admission. Decision-tree analysis identified rib fractures, abnormal respiratory findings, and high injury severity scores as key predictors of ICU admission.</p> Conclusions <p>Although mortality is low, SF are associated with considerable morbidity. Rib fractures, fracture location, and injury severity scores are important prognostic indicators. In this exploratory single-center cohort, ISS and NISS showed better discrimination for ICU admission than TRISS; however, these findings should be interpreted cautiously and require validation in larger prospective studies.</p>