Sensitivity training (ST), which originated in the USA during the late 1940s, has been used as part of training seminars in Japanese corporations since the late 1950s. The possibility of negative psychiatric effects of ST, and especially its role in inducing psychiatric symptoms, is yet to be clarified. A case of a 41-year-old male company worker whose brief psychosis was induced by a sensitivity training seminar held by the company he worked for is presented. In reviewing the psychopathology of the case with records from the ST seminar, we found similarities between the patient's ST seminar and brainwashing situations. Specifically, the patient experienced severe conflict (of thought process) between his Christian beliefs and being labeled a coward at the seminar. We conclude that monitoring of the ST programs is crucial in order to ensure the psychological safety of ST participants in Japan.