Background: Drug addicts are exposed to many psychological and physical injuries due to the problems they experience in their lives; thus, they need training for psychological improvement. The purpose of this study was to evaluate the effectiveness of self-healing training on psychological capital and a sense of cohesion in drug addicts in 2020. Methods: This study was a two-stage quasi-experimental study (experimental and control) in three stages (pre-test, post-test, and follow-up). Using convenience sampling, we selected 30 men willing to participate in the project and randomly divided them into the experimental (n= 15) and control (n= 15) groups. The Psychological Capital Questionnaire and the Sense of Coherence Questionnaire were administered as a pre-test. The experimental group underwent 14 sessions (90 minutes per week) of self-healing training. The follow-up was performed after 45 days. Analysis of the data involved both descriptive and inferential statistics, including mean, standard deviation, and the repeated measures ANOVA. Data analysis was done using SPSS version 24. Results: The results showed that self-healing training had a significant effect on increasing psychological capital, increasing hope with the most effect and resilience with the least effect, as well as increasing participants’ self-efficacy and sense of cohesion (P<0.05). The self-healing training had no effect on optimism. The results remained until the follow-up stage. Conclusion: According to the results, self-healing training can be used as one of the new positive approaches to increase the mental health of drug addicts in treatment centers related to addiction with relatively lasting effects to increase self-care skills.