About 7.1 million school-aged children diagnosed with autism spectrum disorder (ASD; nces.ed.gov, 2020) are being educated in public schools across the United States. To match the rising prevalence of ASD, school districts have increased their reliance on paraprofessionals to assist in meeting the unique needs of this growing population. As a result, paraprofessionals are now assuming a wider range of instructional roles, such as implementing evidence-based practices (EBP), assessing student progress and performance, and utilizing positive behavior supports and interventions. However, paraprofessionals typically have the least amount of education and training to prepare them for these new responsibilities in the classroom. This increasing reliance on paraprofessionals raises concerns regarding their training and preparation to execute these evidence-based practices with students who have the most challenging learning characteristics. The purpose of this study was to understand the roles and responsibilities, and training needs of paraprofessionals supporting students with ASD. This understanding was reached through a non-experimental concurrent embedded mixed-methods design. Surveys and interviews provided insight into the paraprofessionals' roles and responsibilities, training needs and activities, and perceptions of their professional development and supervision. The findings revealed a lack of supervision, initial training, and irrelevant professional development. Paraprofessionals supporting students with ASD requested a training format that was not a "one-size-fits-all" approach, along with content that was individualized to their unique needs, as well as being reflective of the needs of each classroom. Paraprofessionals also desired training concerning behavior management, communication strategies, and natural environment teaching. The results of this study provided several policy implications for training content, frequency, and delivery format, along with recommendations for future research. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]