Background: The hospital length of stay (LOS) relates to the overall status of the patient and the cost of the healthcare. Figuring out possible predicting factors might help the hospital staff to manage fracture patients better and more efficiently. This study sought to determine factors predicting the LOS of trauma patients who underwent orthopedic surgery. Methods: This retrospective cohort study included 255 patients with traumatic injuries of extremities. All patients underwent surgery and had a LOS of more than 24 h. Demographic information, hematological parameters at day 1, comorbidities, and mechanism of injury were analyzed as probable predictors for the LOS. Results: Being female, older age, low hematocrit, high urea and C-reactive protein (CRP)-quantitative values, hypertension, and diabetes were associated with a prolonged LOS. Falling increased the LOS significantly in comparison with the other mechanisms of injury. Based on multi-variable linear regression, the CRP-quantitative level can be considered a strong prognostic factor for LOS. The receiver operating characteristic (ROC) curve analysis was performed to detect the predictive value of CRP-quantitative cutoff plotted against an LOS of more than 5 days. The area under the ROC curve was 0.803. Patients with CRP-quantitative levels greater than 35 mg/l were at risk of prolonged LOS. Conclusion: CRP concentration in trauma patients on the first day of hospitalization can predict a prolonged hospital stay. It seems that inflammatory markers can be accounted as strong predictors of in-hospital events and outcomes like LOS. Moreover, vitamin D level, despite the general assumption, was not associated with LOS.