<p>The text reconstructs the history of Psychology in Brazil, taking as its central axis the relationship between physicians and Psychology — its theories, techniques, and, ultimately, its professionals. Recognizing that history is shaped by its context, it discusses the sociocultural conditions of Brazil’s colonial period, the Empire, and the different stages of the Republic, seeking to interweave them with the medical approach to Mental Health. Against this backdrop, this paper aims at describing how medical studies appropriated the psychological knowledge developed in Europe in the late nineteenth century and it points out how, at the beginning of the following century, psychiatrists began to show interest in and make use of psychological testing, primarily to improve diagnostic discrimination. It then presents the process through which Psychology gained autonomy, following its appropriation by educators. The text later returns to the relationship between physicians and the now-established psychologists within the context of the Psychiatric Reform movement and their joint work in the Unified Health System (SUS). The conclusion points to some trends for the coming years.</p>