Recent advances in chemotherapy have led to the emergence of new types of anticancer agents. With these advances, cases of side effects that have not been witnessed in the past have emerged. The systems of side effect evaluation and their grading have been based on the existing knowledge, such as the CTCAE (Common Terminology Standard for Adverse Events) for evaluating adverse drug reactions in cancer chemotherapy clinical trials. Therefore, new types of side effects may be overlooked or underestimated. Blinatumomab is a bispecific T-cell-engager (BiTE) antibody with specificity for CD19 on B cells and CD3 on T cells. Neurological events, such as neuropathy and encephalopathy, are serious side effects of BiTE antibodies. We encountered a case of a 62-year-old woman who experienced short-term memory impairment and dysgraphia after the first blinatumomab administration for Philadelphia chromosome negative (Ph-) B-cell acute lymphoblastic leukemia (ALL). The CTCAE does not include dysgraphia as a classifier for antibody therapies, such as blinatumomab, and immune effector cell-associated neurotoxicity syndrome, which is defined as a Chimeric antigen receptor T cell therapy-related toxicity; dysgraphia is included in the list of symptoms but is not graded. In this case, the severity of dysgraphia differed depending on the complexity of the letters examined. There is no report that the severity of dysgraphia depends on the letters' complexity, and therefore, it may be overlooked when using simple letters. We have reported the characteristics of dysgraphia in this case and the differences observed when judging different letters.