Guillain-Barré syndrome (GBS) is a rare condition caused by autoimmune damage of peripheral nerves. We describe a case where a man in his 80s presented with subacute, progressive fatigue and weakness. He had received an outpatient work-up for possible haematological malignancy, but eventually presented to the emergency department for worsening weakness. A physical exam and cerebrospinal fluid analysis suggested a diagnosis of GBS. Subsequently, a pathological diagnosis of angioimmunoblastic T-cell lymphoma was made. The patient underwent intravenous immunoglobulin treatment for GBS and was started on cyclophosphamide, doxorubicin, vincristine and prednisone therapy. Prior research has suggested that incident malignancy may be associated with GBS, which may be caused by a paraneoplastic-type phenomenon, malignancy-associated immune dysregulation or an autoimmune reaction triggered by a common exposure. Clinicians should be aware of the possible association between these two conditions and should remain open minded to the possibility of non-infectious triggers for GBS.