This study investigated the extent to which parental Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms impact child and parent outcomes following a multimodal family-school intervention, the Family School Success (FSS) program, when compared to an active-control condition (CARE). Participants were 139 children with ADHD (67% male; 91% non-Hispanic; 77% Caucasian; Grades 2-6) and their primary caretaker (91% female; ages 26-59) who participated in a randomized clinical trial evaluating the efficacy of FSS. Associations were examined between parent-reported ADHD symptoms at baseline and intervention outcomes reported by parents and teachers after treatment and at a 3-month follow-up, including child homework and classroom impairments, child ADHD and oppositional defiant disorder symptoms, parenting behaviors, and parent-teacher relationship quality. Across both treatment conditions, parental ADHD was not associated with parent or child outcomes at postassessment. However, differences emerged between the two treatment groups at follow-up for parents with ADHD, particularly when an empirically supported symptom cutoff was used to identify parents at risk for having ADHD. In FSS, but not in CARE, parental ADHD was associated with declines in treatment gains in the quality of the parent-teacher relationship and the child's homework performance. Parents at risk for ADHD had difficulty maintaining treatment effects for themselves and their child in the FSS intervention but not in CARE. The supportive and educational components central to the CARE intervention may be helpful in promoting the sustainability of psychosocial interventions for children with ADHD who have parents with elevated ADHD symptoms.