Various unconscious mechanisms have been postulated to explain suicidal self-attack including Freud’s suggestions in Mourning and Melancholia (1915/1917), and also in The Ego and the Id (1923). Freud recognized the importance of the Oedipus complex and its role in psychopathology, but he did not link it to suicidal actions. In this paper, the unconscious mechanism for self-attack is reconsidered. It is postulated that in the suicidal state of mind, there is a regression in which previously repressed Oedipal desires begin to resurface. These thoughts/wishes are experienced as intolerable, as they provoke extreme guilt and anxiety about retribution. The accompanying threat of punishment (experienced as castration anxiety) is perceived as insufferable. The anxiety state associated with passively anticipating an impending attack from an externalized source, is countered by the active attack on the dissociated body/self. This self-attack, resulting in suicide, serves as a form of ‘auto-castration’, which is considered to be an appropriate solution for these feelings of guilt, and is believed to be survivable. This unconscious mechanism of suicidal self-attack is explored through the use of clinical examples.