Background Childhood cancer survivors are at risk for long‐term neurocognitive and psychosocial morbidities. Research has seldom examined the relationship between these morbidities; thus, little empirical evidence exists concerning overall salience and how morbidities converge to impair day‐to‐day functioning. An increased understanding of functional impairment resulting from the pediatric cancer experience can inform early risk identification as well as sources for intervention. The purpose of this study was to characterize the frequency/severity of functional impairment and identify significant neurocognitive and psychosocial determinants of functional impairment. Methods Fifty child–parent dyads were enrolled. Children were aged 7–19 years who were at least 2 years postdiagnosis with leukemia/lymphoma and were recruited through a pediatric oncology late effects clinic. Parents completed questionnaires, rating their own adjustment to their child's illness as well as their child's level of functional impairment, while a brief neuropsychological exam was administered to children. Results Twenty‐six percent of the sample evidenced clinically significant functional impairment. Regression analyses indicated that neurocognitive deficits did not predict functional impairment, whereas parental stress was a significant predictor. Conclusions Although children demonstrated both neurocognitive deficits and functional impairments, results favor psychosocial factors, such as parental stress, as a predictor of overall functional impairment. The implications of this study suggest that late effects aggregate to impact day‐to‐day functioning in pediatric cancer survivor populations and parental stress may serve as a marker for heightened risk. The results suggest that broader functional domains, especially school and self‐care domains, should be evaluated and considered when identifying potential targets for psychosocial interventions. Copyright © 2014 John Wiley & Sons, Ltd.