Attention deficit–hyperactivity disorder (ADHD) is a childhood–onset psychiatric condition that often continues into adulthood. The present study was designed to investigate the effect of mindfulness based cognitive therapy (MBCT) on impulsivity of adults with ADHD. The research design of this study was quasi–experimental with pre test and post test of single group. 15 adults with ADHD were selected by convenient sampling method and were receiving mindfulness based cognitive therapy for 8 sessions. Barrat Impulsivity Scale (BIS), balloon analogue risk task and Go–No–Go Test were used as research tools for evaluating of impulsivity of participants in pre and post tests stages. The results of t–test showed a significant decrease in impulsivity of adults with ADHD after treatment with MBCT. In accordance with the findings of this study, MBCT is an effective strategy to reduce of impulsivity levels of adults with ADHD. In cases where reducing of impulsive behavior of adults with ADHD is targeted, MBCT can be used.