Georges Devereux’s ethnopsychiatry is a discipline primarily dedicated to the formalization of the epistemological conditions of an encounter between ethnology and psychoanalysis. This paper will first expound its methodological foundation – complementarism – and then its model of psychological care. Postulating that there exists an incommensurability between the ethnological and the psychoanalytical points of view, complementarism refutes the idea of a conformity between the cultural codes of a disorder’s expression and its subjective appropriation, a conformity between the ethnic and the idiosyncratic. Yet, against his method, Devereux regularly tries to link together the two faces of the symptom, to think them out simultaneously at the risk of making contradictory statements. In this case, the symptom becomes undecidable and Devereux’s ethnopsychiatry ultimately appears as the methodology of a non-relation between disciplines.