Introduction: The overall complication rate after proximal femur fracture surgery is high. This study aims to define the reoperation reasons and outcomes of reoperations after proximal femur fracture surgery in elderly patients.Methods: This retrospective cohort study included patients over 75 years of age who underwent surgery for an intertrochanteric femur fracture and femoral neck fracture between 2014 and 2021. The minimum follow-up was 12 months, or until the patient was deceased. The primary outcome measure was the success of reoperation with regard to fracture type and implant.Results: A total of 89 patients required reoperation for an overall rate of 9.3% during follow-up. Infection was the leading reason for reoperation. Hemiarthroplasty (HA) for intertrochanteric fracture is associated with a high rate of infection compared with HA for femoral neck fracture. The success rate of reoperation due to postoperative infection was poor (46.3%) whereas the success rate for other implant-related complications was favorable (91.6%).Conclusion: The risk of postoperative infection after HA is significantly higher for intertrochanteric femur fractures compared to neck fractures in the elderly population. The limited success after postoperative infection should be taken into consideration in decision-making.