The present article used a pilot study to determine the effectiveness of digital cognitive mindfulness training developed based on dialectical behavioral therapy (DBT) in reducing attention deficit hyperactivity disorder (ADHD) symptoms in children. The sample consisted of 90 children (8-10 years old) diagnosed with ADHD. The participants were randomized into two groups: an experimental group (n = 45) and a control group (n = 45). Results were assessed at three time points: before, after the study, and one month after the end of the study. Regarding ADHD symptoms, the ANCOVA results showed that there were no statistically significant differences between the study groups for inattention and hyperactivity/impulsivity after testing. One month after completion of the program, there was a significant alleviation in symptoms of inattention, executive functioning, learning problems, aggression, and peer relationships. Hyperactivity was the only variable that showed a decrease both post-test and during follow-up. These results suggest that a DBT-based mindfulness program is a promising method of reducing ADHD symptoms in children.