The current experimental pre-/posttest study sought to determine the effect of psychoeducation on the stress levels of parents of children with attention-deficit/hyperactivity disorder (ADHD). A total of 172 parents participated and were randomly assigned to experimental (n = 86) and control (n = 86) groups. There was no significant difference between mean pretest scores of parents in the experimental and control groups on the Caregiver Stress Scale (p > 0.005); however, significant differences were found between pre- and posttest scores in the experimental group after psychoeducation and at 6-month follow up (p < 0.001). There were also significant differences between pre- and posttest scores and pretest scores and 6-month follow-up scores in the experimental group (p < 0.05). In the light of the findings, psychiatric nurses can use psychoeducation programs to support families of children with ADHD to reduce their stress levels. [Journal of Psychosocial Nursing and Mental Health Services, 58(7), 34-41.].