The use of psychology within the context of intelligence or secret services around the world creates ethical issues that inherently erode psychology’s professional standards. The historic case of the East German 'Stasi' secret police provides the opportunity to systematically study such clandestine abuses of psychology, as the Stasi archives are open and accessible. We present information on the structure and function of the Department of Operative Psychology at the former Academy of the Ministry for State Security (Stasi). This includes an outline of its history, corporate identity, curricula, research agenda, and academic (post-)graduation theses. The current article identifies and outlines practical secret police applications such as operational procedures, interrogation techniques, and proscription methods—some of which is subsumed in the Stasi term Zersetzung (decomposition of personalities). Finally, these findings will be discussed with regard to the professional ethics codes of psychologists. We outline recommendations for further scientific examination of this historic case sample and how to prevent this abuse of psychologists and psychological knowledge in the future.