Although school-based preventive parenting interventions have been found to promote children's social-emotional skill development and behavioral functioning, it is important to understand potential barriers to engagement in such programs to ensure that intervention access is equitable and likely to reach those who could most benefit. In the current study, we tested independent and interactive associations between parents' concerns about their child's hyperactivity behavior and their perceived stress in relation to their participation in a preventive parenting intervention, the Family Check-Up (FCU), delivered when children were in kindergarten. Participants were parents of 164 children who were randomized to the intervention group of a randomized controlled trial that took place at five elementary schools. Results indicated that parents who reported higher levels of hyperactivity in their children and high levels of perceived stress were less likely to initially engage in the FCU, but if they did engage, they were more likely to participate more intensively as measured by total treatment time. Parents' motivation to change mediated the association between high parent stress and child hyperactivity in relation to total treatment time. This study has important implications for the use of motivational interviewing strategies to engage parents in school-based, family-centered interventions. [This paper was published in "Journal of School Psychology" v96 p24-35 2023.]