Sigmund Freud’s psychoanalytical theories may be helpful to the analysis of literary works since the contribution of psychoanalysis to literature provides useful interpretative insights. Reading novels, poems and other compositions through the lens of psychoanalysis gives the opportunity to analyse and evaluate these works in their genesis and functioning. The Gothic novel provides many elements such as fear, duplicity, abuse of power and seduction that can be explained according to a Freudian model of literary criticism. In this paper, the personality of Ambrosio, the main character of the Gothic novel The Monk, is investigated with reference to Freud theories concerning the structural or tripartite structure of the mind which conceives the psyche as divided into three parts: Id, Ego and Super-ego. For this purpose, a critical analysis of the text of the novel has been made so to identify all those elements (behaviour, attitudes, emotional reactions, thoughts and utterances) connected to Ambrosio which may illustrate the hidden aspects of his personality and, moreover, explain the reasons of his moral decline.