More than two decades of psychological inquiry has come to associate abnormal disgust responding with a diversity of mental health problems. A maladaptive link between revulsion and depression has long been theorised, but has persisted largely unqualified. In particular, it has been posited that depressive experience may be characterised by dysfunctional self-focused disgust, yet this theoretical proposal, and the notion of “self-disgust” itself, has, for the main, evaded systematic study. Accordingly, in authoring the present thesis, my intention was to produce an exposition of the psychological concept of self-disgust, nested in the broader context of depression. Incorporating mixed-methods of investigation, the current thesis is comprised of three interrelated research projects, designed to provide informative answers to three complementary research questions. First, qualitative methods were used to elucidate the subjective phenomenology of self-disgust within depressive experience. Second, a prospective self-report methodology was harnessed to examine the temporal relations between self-disgust, dysfunctional cognitions, and depressive symptoms. Lastly, three linked experiments were conducted in order to explore whether state self-disgust reactions could be moderated through simple self-affirmation techniques. While this corpus of research indicates that self-disgust is indeed tied to some instances of depression, I appeal to evidence from the former two projects to propose its existence as an independent, enduring, and dysfunctional emotion schema, not adequately characterised by any other established psychological construct. Furthermore, as a lasting phenomenon, I argue that maladaptive self-disgust may function as an antecedent vulnerability for certain instances of depression, and other mental health problems. Finally, a consideration of the experimental findings suggests that self-affirmation may be useful in lessening self-oriented disgust responses, but only under particular conditions. Taken together, this work provides some of the first systematic insight into the hitherto enigmatic psychological phenomenon of self-disgust.