Paraneoplastic syndrome is a broad spectrum of signs and symptoms due to neoplasm, attributed to substances produced by tumor cells, or in response to it. Myasthenia gravis (MG) is a well-known paraneoplastic neurological syndrome (PNS), frequently associated with thymic abnormalities, but rarely reported in patients with lymphoplasmacytic lymphoma. This study presents the case of a 52-year-old Indonesian male patient who was diagnosed with Waldenstrom macroglobulinemia (WM), a rare B-cell neoplasm, after developing a new onset of MG with myasthenic crisis. the patient’s MG features improved with Ibrutinib as a treatment targeted toward cancer. This is the first case report presenting the treatment response of Ibrutinib in WM with myasthenic crisis. The literature was reviewed to explain the possibility of MG as a paraneoplastic syndrome of WM and the treatment response of Ibrutinib for this patient, as well as summarizing previous case reports of concomitant MG and WM. MG should be considered a paraneoplastic malignancy syndrome, including WM, during diagnostic workup. Ibrutinib should also be considered when available to patients, due to its adequate response in both previously treated and treatment naïve patients. © 2024, Indonesian Society of Internal Medicine. All rights reserved.