Fostering student self-determination is now considered an essential element of special education and transition services for children and youth with intellectual disability and/or autism. Yet, little is known about the pivotal role parents might play beyond the school campus in fostering self-determination among their children with developmental disabilities. We examined how 627 parents of children with intellectual disability or autism attending one of 34 randomly selected school districts (a) rated the importance of 7 component skills associated with self-determination, (b) assessed their children's performance in relation to those 7 skills, and (c) evaluated the overall self-determination capacities of their children. Although parents highly valued all of the self-determination skills, the degree to which their children were reported to perform the skills well was fairly low. Several factors predicted higher levels of self-determination, including educational setting, the presence of challenging behaviors, and perceived disability severity. We conclude by offering recommendations for equipping parents to better support their children's self-determination development.