A 4 month-old, 1.9 kg, female, Scottish fold cat was brought to Kırıkkale University Veterinary Faculty Research and Practice Hospital with complaints of progressive dyspnea and exercise intolerance. Dorsal deformation in the caudal part of the sternum and displacement of the heart into the left hemithorax were determined in the clinical and radiographic examinations. In the measurements made on the radiographic images taken before the operation, the frontosagittal index (FSI) and vertebral index (VI) values were measured as 3.5 and 5.1, respectively. An external splint made of PVC material is fixed to the thorax with suture material passed around the sternebrae, in order to correct the sternal malposition in intraoperative treatment. The patient was followed for 8 weeks after the operation. The external splint was removed five weeks after the operation, and the FSI and VI values were measured as 1.4 and 11.3 on the radiographs, respectively. In the postoperative period, it was observed that the patient’s problems such as dyspnea and exercise intolerance disappeared. In animals with bone development yet to be completed, it has been determined that external splint application gives successful results.