Most cases of acromegaly are due to growth hormone (GH)-secreting pituitary adenomas arising from somatotroph cells. Mixed pituitary adenoma and gangliocytoma tumours are rare and typically associated with hormonal hypersecretion, most commonly GH excess. Differentiating these mixed tumours from conventional pituitary adenomas can be difficult pre-operatively, and careful histological analysis after surgical resection is key to differentiating the two entities. There is little literature addressing the possible mechanisms for the development of mixed pituitary adenoma-gangliocytomas; however, several hypotheses have been proposed. It still remains unclear if these mixed tumours differ from a clinical perspective to pituitary adenomas; however, the additional neural component of the gangliocytoma does not appear to modify the aggressiveness or risk of recurrence after surgical resection. We report a unique case of acromegaly secondary to a mixed GH-secreting pituitary adenoma, co-existing with an intrasellar gangliocytoma. CONCLUSIONS Acromegaly due to a mixed GH-secreting pituitary adenoma and intrasellar gangliocytoma is rare.These mixed tumours cannot be distinguished easily from ordinary pituitary adenomas on the basis of clinical, endocrine or neuroradiologic findings, and histological analysis is required for a definitive diagnosis.Surgical resection is usually sufficient to provide cure, without the need for adjuvant therapy.These mixed tumours appear to have a good prognosis although the natural history is not well defined.The pathogenesis of these mixed tumours remains debatable, and ongoing research is required.