Background: Psycho-education is now considered as part of the integrated treatment for bipolar disorder. This study aimed to determine the efficacy of group psycho-education on medication adherence and global functioning of patients with bipolar disorder type I.Methods: 45 patients with bipolar disorder type I were allocated one of the three groups of psycho-education plus pharmacotherapy, pharmacotherapy and placebo plus pharmacotherapy. A psycho-educational program was conducted for the psycho-educational group during 9 weekly sessions. Medication adherence and global functioning of all the three groups were evaluated before the intervention, three months and six months after the intervention using Medication Adherence Rating Scale (MARS) and Global Assessment of Functioning (GAF). ANOVA was performed to examine the data.Results: In the first and second assessments, the mean score of medication adherence and gobal functioning for patients in the psycho-educational group was significantly higher than that in the control and placebo groups (P=0.001). Medication adherence score of the psycho-educational group was increased from 6.27(0.88) to 7.92(1.38). while the mean score of the psycho-educational group increased from 56.6 (3.58) to 64.17 (2.12):, the global functioning reduced from 56.27(3.17) to 54.17(5.08) in the control group and from 56.67 (3.58) to 56 (4.36) in the placebo group.Conclusion: Psycho-educational program plus pharmacotherapy was effective in improvement medication adherence and global functioning of bipolar patients.