Childhood brain tumors and related treatments disrupt the developing brain and have a cascading impact on core cognitive skills and intellectual (intelligence quotient [IQ]) and academic achievement outcomes. Theoretical models for this cascade have been developed based on the literature, but no studies thus far have empirically evaluated the models. The current study aimed to empirically test the two extant models and generate a new data-driven model of the relationships among neurodevelopmental risk factors, core cognitive skills (i.e., processing speed, attention span, working memory), and IQ and achievement outcomes. Fifty-seven adult survivors of childhood brain tumors and fifty-seven demographically matched neurotypical individuals were included in the current study. The average age at brain tumor diagnosis was 8 years, and the average time since diagnosis was 17 years. Three a priori path models tested the hypothesized relationships among variables. Results of the path analyses revealed that the hybrid model best fit the data for both survivors and controls based on all statistical criteria. For survivors, processing speed was the core cognitive skill most widely associated with neurodevelopmental risk factors and outcomes. However, working memory and attention span also had unique contributions to IQ and academic achievement. Processing speed appears to be the central cognitive skill that disrupts the other core cognitive skills of attention span and working memory, and all three make a unique contribution to IQ and academic achievement. This is best demonstrated by a novel neurodevelopmental model that combines components of two earlier untested theoretical models.