Background <p>Fear of progression (FoP) is a significant psychosocial burden for children with cancer and their parents, influencing their quality of life (HRQoL) and emotional adjustment. In this pilot randomised controlled trial (RCT) we present results on feasibility and preliminary efficacy of the family-based therapeutic intervention “Kinder-Progredienzangst” (KIPA), targeting FoP in pediatric oncology.</p> Methods <p><i>N</i> = 29 families with a child undergoing acute cancer treatment or follow-up care completed the program, with participation open to parents alone or to parents and children; ultimately, <i>n</i> = 6 children participated. Eligibility criteria included moderate or high FoP in at least one family member. Families were randomised to either an intervention group or a waitlist-control group receiving treatment as usual. KIPA consists of psychoeducation, anxiety confrontation, and resource activation. Participants completed questionnaires for FoP, anxiety, depression, HRQoL, and posttraumatic stress symptoms (PTSS) at different time points. Participation and retention rates were calculated, and we used Mann-Whitney <i>U</i> tests for between-group comparisons, Friedman and Wilcoxon tests for within-group comparisons and Hedges <i>g</i> for effect sizes.</p> Results <p>Feasibility results showed a participation rate of 23%, with higher participation in acute treatment (51%) compared to follow-up care (15%). Retention rates were 71% overall, with significant variability between settings. Efficacy analyses revealed significant differences in parental FoP between study conditions with high effect size (<i>W</i> = 65.5, <i>p</i>=.023, <i>g</i>=-0.855). Improvements were also noted in PTSS (<i>W</i> = 33, <i>p</i>&lt;.001, <i>g</i>=-1.365), anxiety (<i>W</i> = 59, <i>p</i>=.017, <i>g</i>=-0.906) and mental (<i>W</i> = 217, <i>p</i>&lt;.001, <i>g</i> = 1.619) and physical (<i>W</i> = 180, <i>p</i>=.042, <i>g</i> = 0.834) HRQoL. The pre-post analysis showed a significant reduction in parental FoP in both settings, and the follow-up data indicates sustainability. Effects on children’s FoP were not significant.</p> Conclusion <p>The study showed mixed feasibility—particularly regarding child participation, follow-up enrolment and drop-out during acute treatment—highlighting the need for optimisation before larger trials. Nevertheless, the data provide initial indications that KIPA may benefit parents of children with cancer across both acute and follow-up care settings, a group highly affected by FoP. Given the methodological limitations, the efficacy results should be viewed as preliminary. To demonstrate KIPA’s effectiveness, especially in children, large multicentre trials using reliable RCT designs suitable for acute care settings are needed.</p> Trial registration <p>The trial was retrospectively registered at the German Trial Registry (TRN: DRKS00024106, 04.05.2022).</p>