Abstract Objective Immune effector cell-associated neurotoxicity syndrome (ICANS), an autoimmune delirious condition, affects 37.5% to 77% of individuals during or after chimeric antigen receptor T-cell (CAR-T) treatment for hematologic cancers (Grant et al., 2022). Initial clinical response varies widely but may include apraxia, aphasia, disorientation, and hallucinations (Möhn et al., 2022). Recent research indicates complete symptom resolution in most patients a month post-ICANS onset (Sales et al., 2023). However, a self-report study suggested more than 1 in 3 report persisting cognitive sequelae 1–5 years post-ICANS onset (Rurak et al., 2020). This discrepancy may be due to subtle changes missed by the Montreal Cognitive Objective Assessment (Sales et al., 2023; Möhn et al., 2022). The current case report investigates neurobehavioral outcome post-ICANS via comprehensive neuropsychological assessment. Method Two weeks post-CAR-T therapy, a 53-year-old male exhibited abrupt onset facial palsy and cognitive slowing prompting hospitalization. His wife reported new-onset apathy, atypical behaviors exacerbation (e.g., licking plate), and cognitive lapses (e.g., short-term memory, slowing, repeating questions) with little insight. Neuroimaging revealed supratentorial white matter hyperintensities plus calvarium and R skull base enhancing lesion regression. Results Neuropsychological assessment 10-months post-ICANS revealed subtle executive inefficiencies with family reports of improved yet ongoing social disinhibition and apathy. Conclusions This is the first comprehensive neuropsychological assessment of a patient who developed ICANS post-CAR-T therapy. Neuropsychologists should be aware of delayed cognitive sequelae possibility of this advancing treatment option. Future studies will be useful for patient/family preparation.