Electroconvulsive therapy (ECT) is applied to treatment-resistant mood disorders. Its therapeutic effect on neurocognition remains unclear. We report the case of a 55-year-old man with treatment-resistant bipolar depression who underwent ECT series. We longitudinally monitored his neurocognition with the Brief Assessment of Cognition in Schizophrenia-Japanese version (BACS-J). The patient's scores on all of the BACS-J domains except working memory recovered after the ECT series. Interestingly, his verbal memory, motor speed, and executive function recovered 1 month after ECT, whereas his verbal fluency and attention scores recovered approx. 1 year after ECT. The BACS can be useful for monitoring ECT's longitudinal effects on individuals' cognitive recovery. Further studies with a large sample size are needed to confirm our present findings.