Purpose: This study investigates the rates and causes of treatment discontinuation in one of the two public residential inpatient therapeutic programs for alcohol use disorder in Greece. Both programs are managed by the Department for the Treatment of Alcohol Use Disorder at the Psychiatric Hospital of Attica. The program examined in this study lasts 3 months and is followed by a Comprehensive Community Reintegration phase. Methods: The study analyzed reasons for treatment discontinuation among 402 consecutive admissions to the residential program. Data were collected from the Patient Registry and participants’ Medical and Clinical Records. Results: Of the 402 consecutive admissions, 156 participants (38.8%) discontinued the program during the residential phase. Among these, 37.82% left voluntarily against medical advice, 6.4% left due to physical health issues, and 3.84% left due to a relapse of comorbid psychiatric disorders. The remaining participants were discharged and referred to other care facilities for reasons including forming intimate relationships (13%), verbal abuse (5.12%), unauthorized use of benzodiazepines (11.5%), and testing positive for drugs or alcohol (7.68%). Conclusions: A significant proportion of participants in the residential inpatient therapeutic program for alcohol use disorder discontinue treatment, with over a half leaving voluntarily despite thorough preadmission preparation. This highlights ongoing clinical challenges, including addressing emerging psychopathological issues within the program’s structured environment and enhancing participants’ motivation for treatment.