To best use resources in helping childhood cancer survivors, ascertaining the psychosocial adaptation deficit of the survivor is necessary. Psychosocial adaptation comprises a subjective, self-reflective indicator and objective indicators in terms of education, employment, and other achievements. While deficit is possible due to the trauma caused by cancer and its treatment, research evidence for the deficit is required to ascertain its existence. This study represents such a research endeavor based on a survey of 137 childhood cancer survivors and 101 cancer-free siblings of the survivors in Hong Kong, China. Results reveal weak and inconsistent differences in psychosocial adaptation between the survivor and his or her sibling. The effects of cancer treatment and service involvement on psychosocial adaptation were generally sporadic. Age presented the most pervasive influence on psychosocial adaptation. The results imply a justification for current practices in sustaining the psychosocial adaptation of childhood cancer survivors.