In the 1930s, the concept of "mental hygiene" penetrated Chinese intellectual discourse. Concerned with the treatment and prevention of psychological and psychiatric disorders, mental hygienists believed that the mental health of the Chinese population was essential for achieving national strength and political unity. Under the leadership of the Chinese Mental Hygiene Association, psychologists and social scientists pathologized social deviance as a form of mental illness, thereby justifying their intervention into the private lives of the Chinese people. This article will show how the discourse of mental hygiene in early twentieth-century China was utilized to achieve ideological conformity and extend the authoritarian control of the Guomindang. It therefore suggests that mental hygiene must be considered alongside more general discussions of biopolitics and public health in the Republican period.