Background: Multi-ligament knee injury is common after knee dislocation. There are different approaches for treating multi-ligament knee injuries; however, choosing the best approach is a challenging issue. Objectives: This study aimed to investigate the efficacy of early reconstruction of collateral ligaments and delayed reconstruction of cruciate ligaments in multi-ligament knee injury. Methods: In this prospective study, 24 patients who had a grade 3 tear in one collateral ligament in addition to tears in two other knee ligaments were enrolled. At the first stage, collateral ligaments were reconstructed; after the patient gained full range of motion, reconstruction was done for the cruciate ligaments. Patients were followed-up for one year and postoperative evaluations were conducted through clinical tests, International Knee Documentation Committee scores, and Lysholm scales. Results: Twenty-four patients were entered into the final analysis. Synchronous injury of anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, posterior oblique ligament, posterolateral corner, and lateral collateral ligament had the highest frequency (37. 5%). At the one-year follow-up, the average Lysholm and IKDC scores were 86. 4 ± 3. 5 and 83. 8 ± 4, respectively. Range of motion was normal in all patients at the end of the study. Furthermore, in varus and valgus stress tests, the outcomes of reconstruction were better on the lateral side of the knee than on the medial side. Conclusion: The results revealed that a two-stage surgery consisting of early reconstruction of collateral ligaments and delayed reconstruction of cruciate ligaments have good clinical and functional outcomes in multi-ligament knee injuries.