Objective: Understanding factors that impact child adjustment is imperative. Parental adjustment, parenting behaviors, and environmental factors (e.g., child routines) have been linked to child behavior. In clinical child populations, these factors are particularly important given the increased demands the child’s disorder often places on caregivers. Furthermore, children in clinical populations often engage in increased levels of internalizing and externalizing behaviors both related to and in addition to the core symptoms of their disorder. Two such clinical child populations are Attention Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). Purpose: The first goal of the present study was to elucidate parental and environmental factors that predicted child behavior in ADHD and ASD. Based on Sameroff’s Transactional Model of Development (2009), it was hypothesized that parental adjustment, parenting behaviors and child routines would collectively predict child behavior. A second goal was to examine differences in patterns of association between ADHD and ASD groups. Due to differences in the core symptoms of each disorder, it was hypothesized that the strength of associations would vary between groups. Method: Researchers examined the impact of parental adjustment, parenting behaviors, and child routines on internalizing and externalizing child behavior using parent-report measures (CBCL, CRQ, HSCL-25, APQ) of children ages 6 to 12. Results: Results indicated that for both groups, poor parental adjustment directly predicted externalizing child behavior and indirectly through harsh/disengaged parenting behavior. Fewer warm/supportive parenting behaviors predicted internalizing behavior, and more harsh/disengaged parenting predicted externalizing behavior. Higher levels of child routines predicted internalizing behavior for both groups but had a significantly stronger effect for children with ASD than ADHD. Clinical Significance: Findings have important implications for interventions on several levels (e.g., parental adjustment, parenting behaviors, and environmental supports) in both the ADHD and ASD populations.