Preschool is a particularly opportune time to introduce measures that promote parental school-based involvement, as this is when the initial contact with the school is made. In Québec, a French-speaking province in Canada, voluntary school-based preschools for 4-year-olds have been offered to families in disadvantaged neighbourhoods. A component for parents comprised of 10 activities was developed specifically to promote parent involvement from the beginning of their child's schooling. However, some parents are more likely than others to encounter barriers that curtail their participation in these activities. Seventeen teachers working in preschools for 4-year-olds in targeted areas and 25 of their parents participated in this qualitative study. The study's objective was to identify the barriers to participation among parents whose involvement in school activities during the school year was low. Based on Hornby and Lafaele's conceptual model, a phronetic iterative analysis was used to describe the experiences reported by teachers and parents. Finally, the four main findings emerging from this study were formulated, and avenues for reflection by school-based preschool personnel were put forward.