Arteriovenous fistulas (AVF) are vascular anomalies that can occur after trauma in different parts of the body, including the oral cavity, these abnormalities can trigger several consequences for the affected individual. Such abnormality can be classified as acquired, usually after some trauma or hemodialysis, and congenital. Its diagnosis, in turn, is essential for the management of the patient, avoiding clinical complications. In the oral cavity, although rare, it can affect, especially, the dorsum of the tongue. Ultrasonography is an imaging technique that can be useful in diagnosing AVF in the tongue. This technique allows visualizing vascular structures in real time, assessing blood flow and identifying anomalies such as AVFs. The present study aims to report a case of a 39-year-old female patient who presented a post-traumatic AVF caused by a foreign object in the region of the right dorsum of the tongue. During the professional evaluation, it was possible to use color Doppler ultrasonography to elucidate the presence of venous and arterial flow in the abnormal region, corroborating the clinical findings and being essential to close the diagnosis, denoting the important role of this imaging exam.