A 42-year-old man presented with a two-year history of progressive dysphagia and hoarseness. Esophagogram and endoscopy revealed submucosal mass effect on the upper esophagus. Computed tomography and magnetic resonance imaging revealed an elongated mass in the retrotracheal region of the lower neck with extension to the posterior mediastinum. Partial tumor resection and histopathological evaluation revealed a WHO type B2 thymoma. Adjuvant radiation and chemotherapy were subsequently administered resulting in complete tumor regression. To our knowledge, this is the first report of ectopic retrotracheal thymoma with clinical and imaging manifestations mimicking those for esophageal submucosal tumor. A 42-year-old man presented with a two-year history of progressive dysphagia and hoarseness. Esophagogram and endoscopy revealed submucosal mass effect on the upper esophagus. Computed tomography and magnetic resonance imaging revealed an elongated mass in the retrospective region of the lower neck with extension to the posterior mediastinum. Partial tumor resection and histopathological evaluation revealed a WHO type B2 thymoma. Adjuvant radiation and chemotherapy were also taken together in resulting in tumor regression. To our knowledge, this is the first report of ectopic retrotracheal thymoma with clinical and imaging manifestations mimicking those for esophageal submucosal tumor.