The adult rhabdomyoma (ARM) is an unusual and extremely uncommon tumor. Only 96 cases have been reported. Adult rhabdomyomas are found most often in the region of the base of the tongue, floor of the mouth, larynx, and pharynx. Uncommon locations include the soft palate, uvula, lip and cheek, orbit, and stomach. One prior case of extension of an ARM from the supraclavicular region into the mediastinum has been described as an incidental finding at autopsy. It is important to be aware of and correctly identify this tumor because total excision may be curative. Follow-up must be long-term, as recurrence can occur after 35 years. The authors present a case of an ARM diagnosed during the evaluation and treatment of a symptomatic mediastinal mass. This ARM was found to involve the esophagus and trachea from the inferior constrictors in the neck to the azygous vein in the mediastinum. This case represents a previously undescribed presentation of an ARM. We present a review of ARM and outline our diagnostic, therapeutic, and follow-up plans.