Purpose: Treatment adherence of 95% or higher is recommended for appropriate therapeutic response and improving the function of immune system in HIV positive patients. To the best of our knowledge, there was report of adherence to HAART regimen from Iran. In the present study, we have reported the HAART adherence rate of Iranian HIV positive patients.Method: In a twelve-month period, all patients older than 18 years old who referred to HIV clinic were on HAART regimen enrolled in the study. Beside demographic and clinical characteristics of Iranian HIV positive patients, Adherence to HAART was assessed by self-report and pill count methods at during the three consecutive months of the patients’ visits. Results: The mean of patients’ adherence to HAART regimen based on the self-report method was 69.4%, 64.6% and 62.8% in the first, second and third month of follow up, respectively. The mean of adherence rates in three months followup assessed by self-report (65.5%) and pill count (60.4%) methods were correlated significantly (r=0.93 and p<0.001). Living with family members, changing the HAART regimen and stage of disease had a significant relationship with adherence rates. Conclusion: Although the adherence level of Iranian HIV infected patients is acceptable compared to other countries, the available antiretroviral medications are limited in our country, therefore, encouraging patients to have higher levels of adherence is more important.