Accessory navicular (AN) is a developmental variation of the secondary ossification center of the navicular tuberosity. Ten percent of patients with AN will have pain symptoms that affect walking and life. As the AN changes the position of the posterior tibial tendon insertion, children with AN often have posterior tibial tendon function insufficiency and flexible flat foot. Surgical treatment is often required after failure of conservative treatment. This article reviewed the etiology, clinical manifestations, complications, and treatment methods of AN.