Background & Aims: Drug addiction is one of the serious problems that has caused many concerns in society. In Iran, addiction is highly prevalent among different age groups. Due to diagnostic and reporting conditions, accurate statistics about the number of addicts are not available. However, the population of drug addicts seems to be increasing every year, and this is a serious warning to society. A large number of drug users refer to drug treatment centers every year, but after a while, they tend to use drugs again, which is one of the challenges of society. According to the results of some studies, there is a significant relationship between hope and the cleansing period of drug addicts. Since hope can be a fundamental and motivating factor in drug withdrawal and may play an important role in all stages of drug withdrawal, from action to continuing withdrawal and recovery, it seems that implementing interventions that can raise hope in addicts experiencing withdrawal is necessary for drug withdrawal and its continuation. Therefore, considering that happiness-based programs can increase life expectancy in people, this study aimed to determine the effect of the happiness program on the hope of addicts experiencing withdrawal at the psychiatric center of Zahedan. Materials & Methods: This is a quasi-experimental study. Men aged 18 to 50 years who were admitted to Zahedan Psychiatric Hospital in autumn and winter of 2020 for drug withdrawal comprised the study population. The samples included 92 addicted men. They were selected based on convenience sampling procedure and were randomly divided into intervention (n=46) and control (n=46) groups. Inclusion criteria were no physical symptoms of withdrawal such as pain and restlessness, no psychotic disorder associated with drug abuse, no participation in another counseling program at the same time, and no other addicted family members. More than one session absenteeism and hospital discharge prior to completion of the program were exclusion criteria. In this study, first the control group and then the intervention group entered the study based on non-random sampling procedure. This method was used to prevent the transfer of information in groups. Data collection tools in this study included demographic information form and Miller Hope Scale. This questionnaire was conducted in two stages; pre-test and posttest which was conducted two months later. In the intervention group, eight sessions of the Fordyce Happiness Program were performed every other day. The content of the sessions was prepared based on the Fordyce training program. The Fordyce Happiness Program is a program designed to increase people's happiness and includes eight cognitive components and six behavioral components. The study was conducted based on six Fordyce behavioral components that included components such as increasing activity, increasing social interaction, strengthening close relationships, fostering social personality, creativity, engaging in meaningful works, and self-worth. Data were analyz...