Introduction: Paraneoplastic neurological syndromes (PNSs) are mostly associated with non-epithelial ovarian cancers. We report the case of an advanced high-grade serous ovarian adenocarcinoma, diagnosed during the etiological investigation of a subacute motor-sensory axonal neuropathy variant (AMSAN) of Guillain-Barré syndrome (GBS). According to our literature review, only a single case-control study described a positive association between GBS and cancer.Case Report: A 73-year-old woman was admitted to the emergency department for a progressive symmetrical distal tetraparesis, associated with hypoesthesia and abdominal pain. There was no sign of viral or bacterial infection. Over a period of 10 days, she presented a rapid neurological deterioration with nearly complete paralysis of all extremity, facial, and respiratory muscles.