The current study examines the relationship between attitudes toward illness and quality of life for children with cancer and healthy siblings. Children with cancer (n = 65) and healthy siblings of children with cancer (n = 81) completed self-report questionnaires on quality of life and attitudes toward illness. Parents (n = 115) also completed questionnaires about their children’s quality of life. Illness attitudes were related to both self-report [t(57) = 3.94, p < .001] and parent-report [t(56) = 3.991, p < .01] of child quality of life for children with cancer. Illness attitudes were also related to parent-report of sibling quality of life. These findings suggest a relationship between modifiable cognitive factors, such as attitudes, and quality of life for children with cancer and their families.