Purpose: Preschool children receiving cancer treatment experience decreased gross motor function and challenges in personal and social development. For preschoolers, parents are critical for their child's cancer treatment trajectory, including their participation in physical activity. This study aimed to explore the parents' experiences with a novel rehabilitation intervention, including structured active play for preschoolers with cancer during treatment. Method: Through criterion sampling, 23 parents of 18 preschool children diagnosed with cancer were interviewed from August 2021 until April 2023. A hermeneutic-phenomenological-inspired inductive thematic analysis was performed. Results: Based on 19 interviews with parents, three themes emerged: 1) pushing in the right direction, 2) sharing the responsibility, and 3) creating joyful experiences. The parents experienced that participation in the intervention resulted in physical progress for their child, and the child generally could develop personally and socially. The parents shared a common goal with a healthcare professional, who led the way in their child's physical development and gave them the space to participate with their child. The child actively chose to participate in structured active play, resulting in an altered perception of the hospital experience for both parents and children. Conclusion: The parents’ experiences showed that with the support, knowledge, and expertise of an exercise professional, rehabilitation including structured active play can be a way to integrate movement and physical activity for preschoolers in their cancer treatment trajectory. The repetitive structure of the active play sessions was experienced as motivating for the children and simultaneously challenging their physical, social, and personal development. Trial and protocol registration: ClinicalTrials.gov: NCT04672681. Registered December 17, 2020. https://clinicaltrials.gov/ct2/show/NCT04672681.