Aim
To explore the potential of a structured active play intervention to promote social and personal development in preschoolers during cancer treatment.

Design
A hermeneutic-phenomenological inspired explorative study.

Methods
Participant observations were conducted on 15 consecutively sampled children (aged 1–5 years) from April 2021 to April 2022. Observations were written as narrative scenic descriptions from field notes and were analysed inspired by hermeneutic-phenomenological analysis and using a thematic analysis structure.

Results
Observations were carried out during 67 group or individual structured active play sessions, resulting in 129 scenic descriptions. Observations of the children's emotional, verbal and bodily expressions and social interactions resulted in three main themes: (1) wanting to play, (2) gaining confidence in movement and (3) being part of a group. The findings showed how children, irrespective of age and the severity of their illness, wanted to play and expressed joy of movement. The children's daily physical state fluctuated and influenced their motivation to participate as well as their confidence in their physical abilities. Through structured active play and with support from their parents and healthcare professionals, the children had successful movement experiences and regained confidence in movement, supporting their personal development. Playing together with other children and accompanied by their parents, healthcare professionals supported the children's opportunities to practice social skills, such as turn-taking, waiting and taking charge. Familiarity, recognizability and fun were key motivational components for the children.

Conclusion
Participating in structured active play during treatment has the potential to promote personal and social development in preschoolers with cancer. Parents play a crucial role in supporting the participation of their children.