Regular education teachers' self-efficacy may be negatively impacted due to a lack of professional development and experience teaching students with Autism Spectrum Disorder (ASD). Research links teacher self-efficacy with increased student academic achievement. The purpose of this study was to examine to what degree training on ASD during and following teacher certification and experience had on overall teacher self-efficacy. This one-shot case study was based upon Bandura's theoretical construct of self-efficacy and secondarily on Tschannen-Moran, Woolfolk Hoy, and Hoy's theory of self-efficacy. The Teachers' Sense of Efficacy Scales (TSES) was used to collect data from regular education teachers with experience teaching students with ASD in 1st through 3rd grades in a Southern California school district. After the data were assessed for accuracy, missing data, and outliers, the analysis was conducted on 36 cases. MANOVAs were conducted to assess differences on overall self-efficacy. Separate ANOVAs were used since the overall self-efficacy and the subscores were highly correlated. Though the sample in this study was small (n = 36) for data analysis, the effect size showed that training experience and grade levels had a moderate to large effect on teacher self-efficacy (0.16, 0.13, 0.13 respectively). Therefore teacher self-efficacy has a positive impact on student achievement. Implications for positive social change are self-efficacious teachers increase the academic achievement of students with ASD. In this way, such students can become self-sustaining, dynamic members of the work force and community. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]