Background: The use of metaphors rather than direct suggestions of treatment can help to weaken defense mechanisms against any functional changes and so cause an increase in the effectiveness of therapeutic interventions. Objectives: This research was conducted with the aim of determining the effectiveness of individual metaphor therapy (IMT) in reducing the irrational beliefs and cognitive restructuring of drug addicts undergoing buprenorphine treatment. Patients and Methods: Using a randomized controlled trial (RCT), 100 drug addicts who were referred to MMT/BMT centers in the city of Kermanshah, Iran, from July to September 2014 were selected through single-stage cluster sampling. After excluding 56 patients from the study due to their failure to meet the inclusion criteria, 44 people (37 at the end) were randomly enrolled into the experimental (n = 19) or control groups (n = 18). The SCID-I and the Jones' Irrational Beliefs tests were used as a means of measurement. Ten sessions of IMT (one session per week) were used as the intervention for the experimental group. The controls received routine cognitive restructuring. Data analysis was conducted using a multivariate analysis of covariance (MANCOVA). Results: After adjusting for age and gender, the findings of the study revealed that IMT was significantly effective in reducing the irrational beliefs of approval seeking (P = 0.02), high self-expectation (P = 0.01), frustration reactivity (P = 0.03), anxious over concern (P = 0.02), and perfectionism (P = 0.006). Conclusions: Since IMT can repeatedly neutralize patients' defenses without aggravating their anxiety, and as the therapy can help patients via the development of a new awareness or reformatting the patients' condition, it is recommended that this kind of therapy be used more widely in cognitive restructuring among drug addicts.