Metastatic disease to the pituitary and sellar region as an initial presentation of malignancy is a rare phenomenon. It accounts for approximately one-two per cent of sellar masses. The most common primary malignancies giving rise to pituitary metastases are breast and lung carcinomas. In contrast, neuroendocrine tumours are a heterogenous group of tumours that arise from many organ systems and do not typically metastasise to the pituitary gland. We report a rare example of small-cell neuroendocrine tumour metastasising to the pituitary stalk, which presented with hypocortisolaemia, diabetes insipidus and hyperprolactinaemia. A 43-year-old woman with no prior history of malignancy presented to the emergency department with dizziness, fatigue and refractory hypotension. On further history, she reported amenorrhea and recent weight loss. Biochemistry revealed hyperprolactinaemia (Prolactin 1943 mIU/L) and hypocortisolaemia (Cortisol 50 nmol/L). An MRI brain demonstrated marked thickening and enlargement of the pituitary infundibulum. Over the following month, the patient also developed headaches, nocturia and polydipsia. Repeat MRI showed an increase in size of the pituitary stalk, and a water deprivation test confirmed diabetes insipidus. Trans-sphenoidal resection of the pituitary lesion was performed and histopathology revealed high-grade metastatic small-cell neuroendocrine carcinoma. Post-operatively, both a CT chest/abdomen/pelvis and Positron Emission Tomography identified a lung lesion, which although not amenable to biopsy, likely represented a primary neuro-endocrine carcinoma of the lung. The patient underwent chemo-radiotherapy for the lesion, and cranial irradiation to the site of resected pituitary metastasis. Re-staging CT chest/abdomen/pelvis showed significant reduction in size of the primary lung nodule, indicating good response to chemo-radiotherapy. The patient continues to be followed up with surveillance imaging. This case illustrates the difficulties in diagnosis and management of sellar masses when the presentation is atypical and there is no previous history of malignancy.