This study aims to explore the various defense mechanisms employed by individuals with harmful alcohol use and their implications for psychiatric mental health nursing. Utilizing a literature review methodology, the chapter examines both mature and immature defense mechanisms as classified by Koukias (Principles of psychiatric nursing – mental health nursing (Αρχές ψυχιατρικής νοσηλευτικής – νοσηλευτική ψυχικής υγείας). Broken Hill Publishers LTD, Athens, 2018) in “Principles of Psychiatric Mental Health Nursing.” The findings reveal that mature mechanisms, such as altruism and sublimation, can promote healthier coping strategies and emotional resilience, aiding in recovery. Conversely, immature mechanisms like passive aggression, acting out, dissociation, projection, devaluation, and splitting tend to perpetuate dysfunctional behaviors and hinder recovery efforts. Understanding these mechanisms is crucial for developing tailored therapeutic interventions that support long-term sobriety and emotional well-being. This comprehensive approach underscores the importance of integrating psychological insights into clinical practice to enhance treatment outcomes for individuals with alcohol use disorders.