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Paraneoplastic hypercalcaemia, an uncommon manifestation in ovarian malignancies, exhibits the commonest association with clear cell carcinoma among epithelial ovarian neoplasms. Patients presenting with severe hypercalcaemia of malignancy are considered oncological emergencies, necessitating prompt and aggressive intervention. We present a case of ovarian clear-cell carcinoma (OCCC) that manifests with severe hypercalcaemia as one of its primary clinical features, posing significant challenges to precise diagnosis and preoperative optimisation. The necessity for aggressive fluid resuscitation, calciuresis and meticulous electrolyte monitoring led to an arduous course in perioperative management. Normalisation of the serum calcium levels was promptly noted following primary cytoreductive surgery. This case underscores the importance of including OCCC in the differential diagnosis of unexplained hypercalcaemia, particularly in women presenting with symptoms suggestive of ovarian malignancy. This also emphasises the critical need for early recognition of these paraneoplastic manifestations, facilitating timely diagnosis and treatment initiation, potentially improving prognostic outcomes.