AbstractBackgroundPrecision medicine is projected to become integral to childhood cancer care. As such, it is essential to support families to understand what precision medicine entails.MethodsA total of 182 parents and 23 adolescent patients participating in Precision Medicine for Children with Cancer (PRISM), an Australian precision medicine clinical trial for high‐risk childhood cancer, completed questionnaires after study enrollment (time 0 [T0]). Of the parents, 108 completed a questionnaire and 45 completed an interview following return of precision medicine results (time 1 [T1]). We analyzed the mixed‐methods data comprising measures exploring families’ perceptions and understanding of PRISM’s participant information sheet and consent form (PISCF), and factors associated with understanding.ResultsMost parents were satisfied with the PISCF, rating it as at least “somewhat” clearly presented (n = 160/175; 91%) and informative (n = 158/175; 90%). Many suggested improvements including the use of clearer language and a more visually engaging format. Parents’ actual understanding of precision medicine was low on average, but scores improved between T0 and T1 (55.8/100‐60.0/100;p = .012). Parents from culturally and/or linguistically diverse backgrounds (n = 42/177; 25%) had lower actual understanding scores than those from a Western/European background whose first language was English (p = .010). There was little correlation between parents’ perceived and actual understanding scores (p = .794; Pearson correlation –0.020; 95% CI, –0.169 to 0.116). Most adolescent patients read the PISCF either “briefly” or “not at all” (70%) and had a perceived understanding score of 63.6/100 on average.ConclusionsOur study revealed gaps in families’ understanding of childhood cancer precision medicine. We highlighted areas for potential intervention such as through targeted information resources.Plain Language SummaryPrecision medicine is projected to become part of the standard of care for children with cancer. Precision medicine aims to give the right treatment to the right patient and involves several complex techniques, many of which may be challenging to understand.Our study analyzed questionnaire and interview data from parents and adolescent patients enrolled in an Australian precision medicine trial.Findings revealed gaps in families’ understanding of childhood cancer precision medicine. Drawing on parents’ suggestions and the literature, we make brief recommendations about improving information provision to families, such as through targeted information resources.