Objective To investigate the application value of cone beam computed tomography (CBCT) for the diagnosis of twin teeth. Methods CBCT was adopted as an auxiliary method for diagnosing 1 rare case of twin maxillary second premolar. Data of the clinical examination, X-ray, and CBCT examination were retrospectively analyzed and discussed according to literature reviews. Results Clinical examination revealed that the patient had a complete dentition and the right maxillary second premolar was two completely separated crowns sharing one fused root. X-ray findings showed that right maxillary second premolar was incompletely split and no periapical lesion was found. The exact anatomic structure of the tooth was not shown clearly. CBCT images showed that two crowns joined to form 1 single root at the enamel cementum junction of the teeth and 2 completely separated dental pulp chambers fused to form 1 root at the enamel cementum junction. Conclusion Germination is a rare developmental dental anomaly. It is difficult to diagnose and treat due to complicated structures. The high-end diagnostic imaging modalities of CBCT can assist clinicians to make the correct diagnosis and determine the treatment plan, so as to prevent or reduce potential complications.