Drug abuse leads to physical and psychological problems. Considering the negative and increasing consequences of drug abuse disorder in the community and the importance of this issue, we decided to investigate the efficacy of psychological therapies on reducing drug abuse disorder. This study aimed at the efficacy of dialectical behavioral therapy on blood serotonin levels and cognitive-emotional regulation among drug abusers. It was a quasi-experimental study with a pretest-posttest design and control group. The statistical population consisted of all men with drug abuse referring to Torbat Heydariyeh Adult Drug Abuse Clinic, 40 of whom were selected by simple random sampling for the experimental group (DBT) and a control group. The experimental group was trained for 10 sessions of 90 minutes per week, but the control group was on the waiting list and received no training. Demographic questionnaire, cognitive emotion regulation questionnaire was developed by Granefski and in vitro serum levels of serotonin were used for data collection before and after the intervention. Data were analyzed using the analysis of covariance in SPSS 24 software. The results of multivariate analysis of covariance showed that in the groups of dialectical behavioral therapy, intervention on cognitive-emotional regulation and blood serotonin had a significant effect on post-test (P <0. 05). According to the findings, dialectical behavioral therapy was effective in elevating blood serotonin and cognitive-emotional regulation among drug abusers.