The aim of the present study was to determine the effectiveness of dialectical behavior therapy on emotion regulation and cognitive flexibility in students with social anxiety. In this study, a quasi-experimental method with a pre-test-post-test design with a control group was used, and its statistical population consisted of students with social anxiety who referred to the Educational Counseling Center of District 5 of Tehran in 1403. The research sample consisted of 30 of these students who were selected through purposive sampling and randomly assigned to two groups of 15, experimental and control. Pre-tests were administered to both groups, including the Gross and John Emotion Regulation Questionnaire (ERQ) and the Dennis and Vanderwaal Cognitive Flexibility Questionnaire (CFI). The experimental group underwent dialectical group psychotherapy for 8 sessions of 90 minutes, and the control group did not receive any intervention. Both groups completed the post-test again and the results were analyzed through analysis of covariance. Dialectical group psychotherapy is effective on emotion regulation and cognitive flexibility of students with social anxiety, such that the emotion regulation (cognitive reappraisal and suppression) and cognitive flexibility scores of patients in the experimental group increased compared to the control group (P<0.001). Given that the results support the effectiveness of this approach on the aforementioned variables; the use of this approach is recommended to counselors and therapists who work on anxiety problems.