Parenting self-efficacy is one factor identified as relevant to parent distress and child therapy outcomes. Theories for parenting self-efficacy suggest parents of children with autism spectrum disorders (ASD) may be at risk for lower parenting self-efficacy than other parents. Parents who have low parenting self-efficacy may then have higher risk for poor treatment outcomes. Previous researchers found inconsistent results related to parenting self-efficacy rates for parents of children with ASD. They suggested the results were due to sample sizes, measurement insensitivitiy, comparison groups, and the limited range of children's ages (Fields, 2006; Meirsschaut, Roeyers, and Warreyn, 2010; Palafox, 2004; and Rutgers et al., 2007). In the current study, the researchers invited 598 parents to complete a series of questionnaires. Participants included the parents of children with ASD (n = 57), Down syndrome (n = 24), ASD and Down syndrome (n = 41), emotional and behavioral disorders (n = 287), and no identified diagnoses (n = 189). The parents who participated were 90.2% female and 84.9% Caucasian. Participants from the ASD, ASD with Down syndrome, and Down syndrome groups lived in higher income households (75.2% above $30,000 annually) than those in the emotional and behavioral disorder group (94.1% below $30,000 annually). The questionnaires asked parents to rate themselves regarding parenting self-efficacy, parent distress, parenting skills, social support, and answered demographic questions. Parents from the diagnostic groups also rated their child's behavior and symptom severity. Parents from the ASD, Down syndrome, and ASD with Down syndrome groups answered additional questions found to be relevant in Fields, 2007 (e.g. age of symptom onset, number of siblings, and parent's age). Parents of children with ASD were found to have the lowest rates of parenting self-efficacy across the five groups. ANOVA rejected the null hypothesis that the groups would be the same (F = 8.24, df = 4, 595, p < .01, adjusted R² = .05). The effect size for the relationship between diagnosis and parenting self-efficacy was small to moderate, accounting for 5% of the variance of parenting self-efficacy scores. Pairwise comparisons between groups found parents of children with ASD to have significantly lower parenting self-efficacy than the Down syndrome (mean difference = -3.32, se = .81, 95% CI = -5.86, -.78), and community groups (mean difference = -2.89, se = .58, 95% CI = -4.47 to -1.31). Parents from the community group were also found to have higher parenting self-efficacy than the parents of children with emotional and behavioral disorders (mean difference = 1.43, se = .37, 95% CI = 1.31, 4.47). Parenting self-efficacy was also related to parent distress, social support, parenting skills, and child's age. Parenting self-efficacy may warrant monitoring in the treatment of ASD and may be an important point of intervention in therapy.