Background/Objective Literature shows that there is a circular relationship between children’s ADHD-related behaviors and parenting stress. This systematic review and meta-analysis aimed to understand if mindfulness parent trainings have benefits for both parenting stress and the problem behaviors in children with ADHD. Methods Five databases, CINAHL, Embase, PsycINFO, PubMED, and Web of Science, were searched. Within-group effects at post-treatment and follow-up assessment, and between-group effects at post-treatment were analyzed. Effect sizes (Hedges’ g) were also calculated. Results Ten studies (5 RCTs and 5 non-RCTs) met the selection criteria and were selected for systematic review, and nine of them were included for meta-analysis. Among these 10 studies, five studies involved mindfulness training for both parents and children, while the other five studies involved mindfulness training for parents only. Within-group effects at post-treatment were small-to-large for all outcomes. Hedges’ g ranged between −0.17 [95% CI (−0.98, 0.64)] and 4.70 [95% CI (3.59, 5.81)] for parenting stress; 0.17 [95% CI (−0.03, 0.37)] and 4.03 [95% CI (2.97, 5.09)] for children’s problem behaviors; and 0.20 [95% CI (−0.10, 0.50)] and 2.98 [95% CI (2.16, 3.80)] for children’s ADHD symptoms. Between-group comparisons showed mindfulness parent training was superior to other active controls on all outcomes. Conclusion Findings suggest that mindfulness parent training may be beneficial for parenting stress and children’s ADHD-related behaviors, and due to the small number of studies reviewed, cautions should be taken when interpreting the results.