Mediastinal bronchial cysts (MBCs) are congenital bronchial cysts (CBCs) that mostly occur in the middle and upper mediastinum and rarely in the posterior inferior mediastinum. A case of posterior MBC was reported in a 19-year-old male patient with mediastinal space occupancy on physical examination. Computed tomography (CT) showed an irregular mass near the spine of the posterior inferior mediastinum, which was of mixed density, with nodular calcification at the edge and inside, and no enhancement. Magnetic resonance imaging (MRI) showed heterogeneous hyperintensity on T1-weighted imaging (T1WI) and hyperintensity on T2WI, which were internal to the cord like appearance and showed septation-like hypointensity, mild enhancement of the lesion edge, and septation in the delayed phase after enhancement. The postoperative pathological diagnosis was bronchogenic cyst. In this report retrospectively reviewed the CT and MRI imaging features of this case, as well as those described in the domestic and foreign literature to summarize the imaging findings of atypical bronchocysts in the posterior lower mediastinum to improve the understanding of this disease.