Attention deficit hyperactivity disorder (ADHD) is the most common developmental disorder among school-aged children. A multimodal treatment approach is the most effective approach for ADHD children. Parent intervention group activities help parents with ADHD children develop a good mindset toward their child and help develop skills to design appropriate parenting strategies. Our objective was to study the effect of growth mindset activities on reducing behavioral problems of ADHD children and factors associated with stress among parents of children with ADHD. A randomized controlled trial was conducted and parents of ADHD children aged 7 to 15 years were divided into the experimental and the control groups. The experimental group participated in mindset and communication intervention activities for 3 hours each, while the control group received only initial knowledge and guidance. Baseline data were collected in the beginning of the trial and at 2 and 6 months after starting the trial. Fifty parents with a mean age of 40.14 ± 8.28 years were divided into two groups. After 6 months, the mean mindset scores of the experimental group were statistically significantly higher than those of the control group (p-value = 0.014) and the impulsiveness score decreased by 2.46 ± 1.19 points (p-value = 0.05). The associated factors affecting parenting stress are their own mindset and their child's rebellious behavior. Parent intervention group activities help adjusting parents' mindsets and reduce impulsive behavior in children at 6 months of the trial. A child's rebellious behavior is the best predictor of parental stress, followed by the parents mindset.