Background: Nonunion is one of the medical conditions challenging the trauma specialists. Timely identification of people at high risk of nonunion is important to improve the prognosis of patients.Methods: We retrospectively analyzed the demographic and laboratory hematological characteristics of 338 patients with either clavicle or femoral fractures treated with ORIF in Shandong Provincial Hospital affiliated to Shandong University from January 2010 to May 2019. Descriptive statistics, univariate regression analysis, and multivariate regression analysis were conducted to confirm the independent factors associated with nonunion after ORIF.Results: The overall nonunion rate among the patients investigated in this study was ~6.8%, while the nonunion rates were 5.6% and 10.3% in clavicle and the femur fractures, respectively. Results of the univariate logistic regression analysis showed that the serum fibrinogen concentration (FIB), the hemoglobin count (HGB), the lymphocyte absolute value (LYMPH), the coefficient of variation of red blood cell distribution width (RDW-CV), the American Society of Anesthesiologists (ASA) classification, and the mechanism of injury were related to the occurrence of nonunion (p < 0.05). Results of the multivariate regression analysis showed that FIB (OR = 1.64, 95% CI of 1.14 to 2.36, p < 0.01), LYMPH (OR = 0.34, 95% CI of 0.15 to 0.77, p < 0.01), ASA classification (OR = 3.52, 95% CI of 1.20 to 10.31, p = 0.02), and injury mechanism (OR=3.13, 95% CI of 1.20 to 8.21, p = 0.02) were independently associated with the occurrence of nonunion.Conclusions: Our study has revealed that FIB, LYMPH, ASA classification, and injury mechanism are independently related to the occurrence of nonunion after ORIF, providing important guidance for clinicians to identify patients with high risk of nonunion in time, ultimately improving the prognosis and quality of life of patients.