The objectives of this research was to assess the relationship between parental capacity and quality of life of children with cancer. Parental capacity, such as overprotection (OP), perception of child vulnerability (PCV), and parenting stress (PS), can affect the relationship between parents and their children with cancer. It influences children?s emotional, behavioral, and social functions. This research was an analytical cross-sectional research carried out to 74 children in Haji Adam Malik Hospital Medan from November ? December 2020. Interviews were conducted to assess children?s quality of life by PedsQL and parental capacity with Kolmogorov Smirnov test. Correlation tests were done by Pearson and Spearman analysis. The mean value of PS was 103.32. The median score of OP was 48 (28 ? 68), PCV was 17 (10 ? 22), and children?s quality of life was 77.88 (50.55 ? 98.15). There was no significant relationship between OP (p = 0.469) and PCV (p = 0.781) with quality of life. However, significant relationship was observed between PS and quality of life (p <0.001) of children with cancer.