Education in American schools is driven by the No Child Left Behind Act (2001) with the Individuals with Disabilities Education Improvement Act (2004) ensuring that educators provide students with disabilities a grade-aligned education. Recently, the Common Core State Standards (CCSS) have been adopted as a way to provide consistency of content for students across the U. S. One priority component established in the CCSS is for vocabulary instruction to occur across content areas. Understanding effective methods for teaching mathematical vocabulary to all students is needed, especially students with severe disabilities. Research has identified Direct Instruction (DI) effective for teaching students with severe disabilities components of literacy; however, no research exists on how to teach mathematics vocabulary to young students with autism. The purpose of this research was to determine if DI is an effective method for teaching early elementary mathematical vocabulary to students with autism. Results indicated that DI shows promise with students possessing prerequisite skills and learning behaviors, such as attention and engagement, when introducing new information. However, some students continue to require explicit, systematic instruction in a one-to-one format to make progress with novel skills. Information gained from this research suggests that DI in small group may be effective during maintenance and generalization for young students with autism. Additionally, when teaching new skills to students with autism, it is necessary to begin at their current level of communication.