Garré's sclerosing osteomyelitis is a distinctive type of chronic osteomyelitis that mainly affects young adults and is difficult to differentiate from other bone diseases. Here, we report the case of a 27-year-old woman who presented with facial swelling and pain and was treated at a local dental clinic with a root canal therapy of the lower right second premolar. With no improvement in her condition, she was transferred to our hospital for further treatment. Physical examination, radiographic examination including dental X-rays, computed tomography (CT), and a whole-body bone scan were performed. From our investigation, a differential diagnosis was established, and the pathologic diagnosis confirmed our impression of Garré's sclerosing osteomyelitis. The patient was treated with medication and endodontic treatment; close follow-up revealed that the treatments were successful.