Background <p>Intramedullary nailing (IMN) is considered the gold standard surgical technique for the management of femoral shaft fractures. Nonunion is characterized by the absence of complete healing within nine months post-injury or the lack of any radiographic evidence of callus formation within three months. In this study, we aimed to evaluate the effects of postoperative fracture interval and translation and other factors on bone union in femoral shaft fractures treated with IMN.</p> Materials and methods <p>A total of 87 patients with femoral shaft fractures who underwent IMN surgery in our clinic between January 2017 and January 2024 were included in this retrospective study. The patients were followed postoperatively through routine clinical and radiological assessments.</p> Results <p>Open reduction was associated with a 3.7-fold higher risk of nonunion compared to closed reduction. No significant correlation was observed between healing time and either the fracture gap in the anteroposterior and lateral planes or the nail-to-canal diameter ratio. In the regression analysis, with healing time as the dependent variable, both open reduction and anteroposterior translation emerged as independent predictors of delayed union (<i>p</i> &lt; 0.001).</p> Conclusions <p>Our study results showed that the rate of open reduction was higher in patients with nonunion and those with open fractures and those undergoing open reduction had longer healing times. We also observed a positive correlation between translation values in the anteroposterior and lateral planes and healing time, with increased translation leading to longer healing durations. These findings indicate that open reduction and increased fracture translation, particularly in the anteroposterior plane, are significant factors influencing delayed union and nonunion in femoral shaft fractures treated with IMN.</p>