Heterotopic brain presenting as a giant, growing, single locular cyst at the parapharyngeal space has not been reported before, to our knowledge. We present such a case, with MR imaging findings, in a 13-month-old girl. A well-demarcated giant cystic mass was noted in the left parapharyngeal space from the skull base to the submandibular region. Airway compression and deformity of the left mandible with subluxation of the temporomandibular joint were noted. The cyst contained a clear fluid that was isointense to CSF with all pulse sequences. Wall enhancement was noted on contrast-enhanced T1-weighted images. No connection to intracranial structures was noted. Histologic findings were compatible with neuroglial heterotopia.