Background Childhood cancer affects the whole family. Illness‐related stressors increase the risk for poor family communication, affecting the family's well‐being. Siblings describe worry and poor illness‐related information. As there are few evaluated family interventions in pediatric oncology, this study aimed to pilot‐test a family‐centered intervention, the family talk intervention (FTI), in pediatric oncology. This paper examined the feasibility in terms of acceptability from the siblings’ perspectives. Methods This study derives from a pilot study of 26 families including 37 siblings recruited from one pediatric oncology center. Standard FTI comprises six meetings with the family, led by two interventionists, with the main goal to facilitate family communication on illness‐related topics (e.g., prognosis, the invisibility of healthy siblings). This paper focuses on interview and survey data from siblings after participation in FTI. The study is registered at ClinicalTrials.gov (Identifier NCT03650530). Results The siblings, aged 6 to 24 years, stated that the interventionists made the meetings feel like a safe environment and that it was a relief for the siblings to talk. They reported that FTI helped the family talk openly about illness‐related topics, which they felt led to increased family understanding and improved relationships. The siblings described that FTI also helped them with their school situation. The majority of the siblings reported that FTI came at the right time and involved an appropriate number of meetings. Conclusion According to the siblings, the timing, content, and structure of FTI were appropriate. FTI showed benefits for both the siblings and each family as a whole.