A two-month-old male guinea pig (376 grams) presented with a right hindlimb lameness following accidental trauma. Clinical examination revealed misalignment, crepitus, and loss of function in the right hindlimb. Radiographic evaluation confirmed a closed, complete oblique fracture in the proximal third of the femur. General anesthesia was induced using intramuscular dexmedetomidine, butorphanol, and isoflurane via face mask. Surgical intervention was performed via open reduction and internal fixation (ORIF) with a retrograde intramedullary (IM) pin and Type 1a external skeleton fixation (ESF), consisting of two horizontal ESF pins, stabilized with a fessa tube. Postoperative management included oral marbofloxacin, meloxicam, and gabapentin. Fracture healing was monitored radiographically and clinically at 2-3 week intervals. Callus formation was first observed at the fracture site three weeks post-surgery, and the ESF was removed at this time. Functional recovery was noted by 4-5 weeks after surgery, with the guinea pig demonstrating normal locomotion. The IM pin was removed at 7 weeks, and the animal regained full mobility. The use of tie-in ESF in this case provided effective stabilization for a proximal femur fracture. Radiographic and clinical assessments demonstrated satisfactory healing, with no complications such as malalignment or dislocation. This case highlights the efficacy of tie-in ESF as a stabilization method for femoral fractures. Although IM pin fixation alone has been reported in similar cases, the specific nature of the proximal fracture, along with sharp bone edges at the fracture site, suggests that tie-in ESF offers superior stabilization in this instance.