Purpose Although posterior cruciate ligament avulsion fracture is a rare condition, but lack of its treatment results in knee instability. Identification of functional and clinical outcomes after open reduction and internal fixation was the main goal of this research. Methods Thirty-one patients, underwent operation due to isolated tibial posterior cruciate ligament avulsion fracture, were followed-up for a mean of 24 months (range 13-44 months). Outcome was evaluated by International Knee Documentation Committee form. Results The most common cause of injury was motor vehicle accident (in 26 cases). Finally, 74.2% of cases had normal or nearly normal grade. Also, no one was graded as D (severely abnormal). The functional result was better when the avulsed fragment size was bigger (p value 0.037). Conclusion Treatment of tibial posterior cruciate ligament avulsion fracture through open reduction and internal fixation with screw and washer results in acceptable functional outcome in about three quarters of cases.