Background: Femoral fractures involving the lesser trochanter that extend distally up to 5 cm are known as sub-trochanteric fractures. The present study was conducted to assess outcome of sub-trochanteric femur fractures managed with long proximal femoral nail. Materials & Methods: 70 patients with sub-trochanteric fractures of femur of both genderswere managed with long proximal femoral nail. All patients were assessed functionally by Harris Hip Score. Results: Out of 70 patients, 38 were males and 32 were females.Intra operative complicationswere failure to achieve closed reduction in 1 case, fracture of lateral cortex in 2 patients, failure to put anti-rotation screw in 1 case, guide wire breakage in 3 cases. Delayed complications were knee joint stiffness in 2 cases, delayed unionin 1 case, implant failurein 2 cases, hip joint stiffness in 3 cases, superficial infectionin 1, varus angulation in 1 patient. The difference was significant (P< 0.05). Conclusion: For subtrochanteric femur fractures, the long PFN is a dependable implant with a high rate of bone union and little soft tissue injury. Although intramedullary fixation offers advantages in terms of biology and biomechanics, the procedure is technically complex.