Hashimoto's encephalopathy, a steroid-responsive encephalopathy, presents with cognitive deterioration, psychiatric symptoms, and seizures and is often associated with elevation of anti-thyroid peroxidase antibodies or thyroid dysfunction. Because of the absence of a gold-standard diagnostic test and serological marker of disease, improvement in cognitive impairment is an important sign when assessing response to corticosteroid treatment. The purpose of this case study is to present a methodology for tracking neurocognitive functioning using computerized testing (CNS Vital Signs) in a 14-year-old girl with Hashimoto's encephalopathy. Computerized neuropsychological testing was done prior to commencing corticosteroid treatment, as well as at 7 follow-up assessments over 1 year. Improvement in cognitive, psychological, and behavioral functioning heralded a response to treatment, which was sustained during tapering of medication. Computerized neuropsychological testing seems to be a viable tool for tracking cognitive functioning (when rapid assessments are desired) and assessing response to corticosteroid treatment in Hashimoto's encephalopathy.