We examined the relationship between initial parenting stress and change in parental responsivity for 56 culturally and socioeconomically diverse families in a 12 week randomized control trial of Pathways Early ASD Intervention. Families were randomized into the Pathways (n = 32) or treatment-as-usual (TAU n = 24) group. Overall, Pathways parents experienced decreased stress, while TAU parents experienced an increase. The relationship between initial parental stress and change in parent responsivity was moderated by group membership. Pathways parents became more responsive but responsivity was not influenced by initial parental stress. In contrast, responsivity was negatively affected by initial parenting stress in the TAU group. Results are discussed in terms of components of a parent-mediated ASD intervention that may reduce parental stress.