Theoretically-driven investigations on the potentially modifiable predictors of individual differences among newly-diagnosed pediatric cancer patients may facilitate the Identification of children at risk for adjustment problems. Within a risk and resistance conceptual model, family functioning was investigated concurrently and prospectively as a predictor of adjustment in newly-diagnosed pediatric cancer patients at Time 1 (within 1 month after diagnosis). Time 2 (6 months postdiagnosis), and Time 3 (9 months postdiagnosis). The family relationship dimensions of cohesion and expressiveness most consistently predicted the psychological and social adjustment of children with newly-diagnosed cancer over a 9-month period after initial diagnosis. These findings are discussed in terms of the treatment implications for enhancing child adjustment to newly-diagnosed cancer and biomedical treatment.