Background: Parents' emotional states, self-efficacy, and perceived social support levels are crucial elements to consider when planning treatments for children with autism spectrum disorders (ASD). High levels of parental stress, depression, anxiety and low levels of parental efficacy and social support may disrupt the role of parent involvement in early intervention programs. In this study, Hanen's "More Than Words" (HMTW) intervention was provided to a group of parents with children who had been diagnosed early with ASD. Method: Fourteen parents and their children with ASD (four girls and ten boys) were enrolled in the study. The primary impact of the HMTW intervention on parents' emotional states, self-efficacy, interactional behaviors, and perceived social support levels and its secondary effect on children's communication development was investigated in five different time intervals and in three different conditions (pre-intervention, post-intervention, and follow-up). Results: The results indicated that the rate of change in the levels of parents' self-efficacy, state of anxiety, parental stress, parental interactional behaviors, and childrens' verbal language performances and interactional behaviors was statistically different in the post-intervention period when compared with the pre-intervention period (p < .05). Conclusions: The HMTW intervention did not only have a positive effect on parents, but also on children with ASD in this study. What this paper adds: This research was an extension of the previous "Hanen's More Than Words" efficacy studies to examine the program's primary effect on parents' emotional states, self-efficacy, interactional behaviors, and perceived social support levels and its secondary effect on children's interactional behavior and language development. The findings of the study confirm that the program has the potential to increase parents' sense of efficacy and the quality of parent-child interactions. The main conclusion is that parents, as the main caregivers, should be involved in the treatment of their young children with ASD.