A case of progressive facial weakness associated with an anomaly of the internal auditory canal and labyrinthine segment of the facial nerve is documented with clinical, radiological, and surgical findings. Each portion of a double internal auditory canal (aberrant facial nerve canal) was found to contain a portion of the facial nerve, and each portion of the facial nerve was explored because a tumor was suspected to be the cause of the progressive weakness. However, no mass was found. The embryologic factors that may lead to such an abnormality and the pathophysiologic mechanisms that may have resulted in the facial weakness are discussed.