This chapter compares Pierre Janet’s views on the dissociative responses to psychological trauma with those influenced by the psychoanalytic theory of defence mechanisms, in order to examine their accordance with some findings of contemporary psychotraumatology studies. We agree with Russell Meares’s statement that both psychoanalysis and Janet’s psychological analysis seem often compatible with clinical observations and with data from contemporary neuroscience (Meares, 2012a, p. 27). Our aim, therefore, is not to argue in favour of one of those theories and against the other. Rather, we mean to highlight the relevance of Janet’s ideas for contemporary psychotraumatology without implying that the psychoanalytic ones are less – or more – relevant.95