The purpose of this study was to examine parenting stress over time and its relationship to adaptive behavior and observed child behavior during language interventions in a sample of 113 toddlers with significant developmental delays. The data included are from two longitudinal studies of language outcomes following augmented or spoken language interventions (Romski et al., In preparation; Romski et al., 2010). We found that parenting stress was elevated relative to the normative sample, however, there was no relationship between parenting stress and observed child behavior. Lower child adaptive behavior was associated with both higher parenting stress and more observed child challenging behaviors. Our results suggest a complex picture of the relationships between parenting stress, child challenging behavior, and child adaptive behavior, in which child adaptive behavior has a stronger influence on parenting stress among parents of toddlers.