Brunner's gland adenoma is a rare, benign, small-bowel neoplasm. In a few reported cases, it can cause gastrointestinal hemorrhage and can be associated with cellular atypia. We report an 84-year-old woman with a 12-mm Brunner's gland adenoma in the second part of the duodenum that was successfully removed with a saline injection-lift technique using a hot snare, followed by placement of clips to prevent postpolypectomy bleeding. Pathological examination revealed Brunner's gland adenoma with high-grade dysplasia and oncocytic features with negative resection margins. The patient recovered uneventfully. Brunner's gland adenoma is traditionally considered a benign lesion, and few cases in the published literature have reported Brunner's gland adenoma with dysplasia or neoplasia. This suggests a dysplastic stage in the natural history of Brunner's gland adenoma and questions the malignant potential of such lesions.