Rozanolixizumab, a novel therapeutic medication for myasthenia gravis (MG), is a humanized monoclonal antibody against the neonatal Fc receptor. Sold under the brand name Rystiggo, it is the first treatment that the U.S. Food and Drug Administration has approved for adults with MG positive for either anti-acetylcholine receptor (anti-AchR) or anti–muscle-specific kinase (anti-MuSK) antibodies. A 32-year-old woman with MG positive for anti-MuSK antibody presented to the emergency department with a severe headache, neck stiffness, photophobia, and fever after receiving her first dose of rozanolixizumab. Medication-induced aseptic meningitis was diagnosed. This case highlights drug-induced aseptic meningitis as a serious adverse effect of rozanolixizumab.