This study aimed to gain more insight in the sources of daily parenting among mothers of children with autism spectrum disorder (ASD). Specifically, we examined associations between daily variations in child behavior, mothers’ psychological needs, and mothers’ controlling and autonomy-supportive parenting. Moreover, the study examined the potential mediating role of daily vitality and stress within these associations. In total 41 mothers (Mage = 41.84 years) of children with ASD (Mage = 10.92 years, range 7–15) participated in a 7-day diary study. Multilevel structural equation modeling revealed that both daily child behavior (i.e., externalizing problems and prosocial behavior) and mothers’ psychological needs relate to day-to-day variation in parenting behavior. Daily stress and vitality played an intervening role in most of these associations.