Objectives: <span class="fontstyle2">Diabetes is a chronic, multifaceted and threatening disease which has significant psychological complications. The purpose of this study was comparing the efficacy of Acceptance and Commitment Therapy (ACT) and Dialectical Behavioral Therapy Skills Training (DBT-ST) on cognitive emotion regulation in patients with type II diabetes. Method: <span class="fontstyle2">The design of this quasi-experimental research was a pretest-posttest with a control group. The statistical population of the study included all patients with type II diabetes referred to Baghban (Touba) Medical Clinic in Sari in 2019, among whom 45 patients were selected through the convenience sampling method and then randomly assigned into three groups. The first group received ACT, the second group received DBT-ST, and the third group was considered as a control group. Data were collected using a 36-item Cognitive Emotion Regulation Questionnaire (Garnefsky et al., 2001) in three stages of pre-test, post-test, and follow-up, and were analyzed by repeated measurement variance analysis. Results: <span class="fontstyle2">The results showed that ACT and DBT-ST were significantly more effective on cognitive emotion regulation for the experimental groups compared to the control group (effect sizes 0.911 & 0.967, respectively). The effectiveness of DBT-ST compared to ACT was more significant on cognitive emotion regulation scores (effect sizes 0.967) at (P>0.01). Conclusion: <span class="fontstyle2">Based on the results of this study, it can be concluded that ACT improved psychological indexes and mental health of patients with type II diabetes due to acceptance of unfavorable emotions and thoughts, commitment, and DBT-ST for emotion regulation and mindfulness components
