To inform the development of scalable and sustainable fundamental motor skill interventions for children with Down syndrome, this study examined the feasibility and preliminary effectiveness of Project Skill Intervention Implemented by Parents (Project SKIP), a web-based, parent-mediated intervention intended to improve ball skills among children with Down syndrome. Twenty-four families enrolled in the study (including 13 boys and 11 girls; M age = 4.92). Fourteen children were assigned to an experimental group and participated in the 6-week intervention, and 10 children served as the inactive comparison group. The Test of Gross Motor Development-3 was administered preintervention and postintervention. In addition, parents of children in the experimental group completed a postintervention survey to assess their perceptions of Project SKIP. Following the intervention, there was a significant improvement in ball skills (p = .023, d = 0.86) for children in the experimental group, whereas the comparison group did not show significant improvement. Moreover, parents perceived Project SKIP to be feasible and effective; all parents reported being satisfied with their overall experience in the program, and 11 parents indicated that their child’s fundamental motor skills were positively influenced by the intervention. Engagement was high, with the majority of parents (n = 8, 57%) interacting with Project SKIP content three to four times a week.