The authors share their experience on a collision tumor of growth hormone (GH)-secreting adenoma and gangliocytoma in the pituitary gland, which was reported by few articles in the literature. Also, an intraoperative view of this tumor, operated via endoscopic endonasal transsphenoidal approach, is presented for the first time. A 39-year-old female patient was admitted with clinical manifestation of acromegaly present in a 2-year period. Laboratory investigations revealed high levels of GH and insulinlike growth factor 1. Sellar computed tomography scan and magnetic resonance imaging showed a sellar mass diagnosed as a pituitary adenoma. Based on clinical, biochemical, and radiologic evaluations, GH-secreting pituitary adenoma was diagnosed and operated by endoscopic endonasal transsphenoidal approach achieving total removal of the tumor. Histopathologic examination revealed a collision tumor of GH-secreting adenoma and gangliocytoma. Postoperative radiologic and biochemical investigations showed no residual tumor and total remission. The endoscopic endonasal transsphenoidal approach promotes a close intraoperative view of sellar pathologies. We believe that a detailed histopathologic workup is necessary to diagnose collision tumors, because even a close intraoperative view does not facilitate to differentiate these tumors from a regular pituitary adenoma.