Introduction: Psychological factors such as negative emotions play an important role in the management of diabetes mellitus one of the most common chronic diseases. The purpose of this study was to investigate the effectiveness of emotion regulation training in improving emotion regulation strategies and glycemic control in patients with type II diabetes. Materials and Methods: This quasi-experimental study had a pretest-posttest design. The study population included 40 patients with type II diabetes, selected by convenience sampling from the Samen Alaemmeh charity  center and randomly divided in two, the experimental and the control, groups (n=20 each). Subjects in both groups completed the Garnfski`s Cognitive Emotion Regulation Questionnaire (2001, CERQ) both pretest and posttest, and Hb (A1C) was also measured at these times in both groups. Eight 90 minute sessions of emotion regulation group therapy were conducted in eight weeks. Data were analyzed by covariance analysis method with software spss-18. Results: Data analysis showed that emotion regulation strategies and glycemic control in the experimental  compared to the control group, at posttest were decreased (p<0.05). Conclusion: Based on the results of this study, emotion regulation training could be an effective method for improvement of emotion regulation problems and glycemic control in patients with type II diabetes.