Purpose/Objective: To examine mastery motivation and executive functions or behaviors as predictors of adaptive behavior in adolescents and young adults with congenital neurodevelopmental conditions. Method: Participants were 2 groups of adolescents and young adults, ages 13–29, including 43 with cerebral palsy and 36 with myelomeningocele living with a parent or caregiver. Participants completed measures of mastery motivation, executive functions or behaviors, and a measure of adaptive behavior. Results: Group differences in mastery motivation, executive functions and executive behaviors, and adaptive behavior profiles were not significant. Mastery motivation, executive functions, and executive behaviors explained a significant portion of variance in adaptive behavior. Conclusions: Findings highlight the importance of assessing and addressing motivational and executive needs in developing interventions to promote independence. Findings also suggest the need for more comprehensive assessment of adaptive behaviors that include the ability to self-direct others in the completion of tasks necessary for successful daily functioning.