The relationship between maternal parenting and the prosocial behavior of a child with autism spectrum disorder (ASD) was tested cross-sectionally (Study 1) and longitudinally (Study 2). In Study 1, maternal prosocial behavior was moderately associated with child behavior, and maternal positive parenting completely mediated this relationship. In Study 2, we found that the association between guidance (T1) and maternal prosocial behavior (T2) was significant, as were the longitudinal and mutual associations between high control and child prosocial behavior. However, a mediating effect of any component of parenting was not found in the longitudinal data. These results suggest an important role for maternal parenting in the development of prosocial behavior in children with ASD.