This report aims to present a rare case of severe hyponatremia induced by syndrome of inappropriate antidiuretic hormone secretion (SIADH) following chemotherapy in a patient with small cell carcinoma of the cervix (SCCC). It also reviews the existing literature on this rare phenomenon. A 45-year-old female with SCCC developed acute symptomatic hyponatremia (sodium level 110 mmol/L) three days following cisplatin-based chemotherapy. SIADH was diagnosed, and the patient required intubation and admission to the intensive care unit due to severe agitation and confusion. Despite initial correction of sodium levels, the patient developed recurrent hyponatremia after subsequent chemotherapy cycles that was refractive to first line agents. She required the use of Tolvaptan, a vasopressin type 2 receptor antagonist, for the management of hyponatremia. This case highlights the rare occurrence of severe SIADH in a patient with SCCC, underscoring the complexity of managing electrolyte disturbances in the context of both paraneoplastic syndromes and chemotherapeutic side effect. The severity of our patient's presentation calls attention to the importance of early recognition of SIADH in the differential diagnosis of oncology patients with altered mental status and confusion. Post chemotherapy sodium surveillance could lead to improved patient outcomes, as well as monitoring for signs and symptoms of hyponatremia.