Background: The mothers of children with attention-deficit hyperactivity disorder tend to experience depression at higher levels because of the poor social interaction and deviant behaviors of their children. These depressed mothers often harm themselves and negatively impact their family and community. Purpose: This study examines maternal depression and its related factors in the mothers of school-aged children with attention-deficit hyperactivity disorder. Methods: A cross-sectional study with a purposive sampling of 100 mothers of school-age children with attention- deficit hyperactivity disorder was developed. Data were collected using a structured questionnaire that included the Parenting Stress Index (PSI), social support scale, and the Beck Depression Inventory (BDI). The Pearson product moment correlation and stepwise multiple regression were used to analyze data. Results: The findings showed that almost half of the mothers with school-aged ADHD children suffered higher parenting stress and that 34% required professional psychiatry referral. In addition, 40% of the participants suffered from depression. Higher levels of parenting stress were associated with a higher incidence of depression (r=.647, p＜.001). Participants with better social support had lower depression levels (r=-.327, p＜.01). 'Parenting stress' and having a monthly total household income of ≤ NT$40,000 were significant predictors of maternal depression. 'Maternal stress' was the most significant predictor, with a total explained variance of 41.9% (R^2 change=41.9%). Conclusions: The results of this study are intended to help medical staff better care for the mothers of school-aged children with ADHD. These results will assist in the evaluation of maternal depression, parenting stress, and levels of required social support. It will especially help in the evaluation of maternal depression symptoms of those mothers of low socioeconomic status with high parenting stress. Providing these mothers with parental training, education on effective parenting and discipline strategies, and better social support may effectively reduce maternal depression, which will help minimize the negative impacts of this depression on the family and the community.