Mathematics Anxiety (MA) and Mathematics Teaching Self-Efficacy (MTSE) have been reported as factors related to teachers' mathematics instruction. This study investigated MA and MTSE in in-service elementary teachers' virtual mathematics instruction. A comparative case study design was used to understand the relationship between MA, MTSE, and their virtual mathematics instructional practices. Two in-service elementary teachers from an urban public charter school district in a large metropolitan city in the Midwest participated. I employed qualitative methods to examine the results from the Abbreviated Mathematics Anxiety Rating Scale (AMAS), an adapted version of a researcher-developed instrument called the Mathematics Teaching and Mathematics Self-Efficacy Scale (MTMSE), interviews, teacher classroom observations, post-observation interviews, and a fraction simulation task to learn how teachers approached virtual mathematics instruction. Results indicated the in-service elementary teachers had low to moderate MA and high MTSE when teaching elementary mathematics concepts. However, if they were to have taught higher-level mathematics concepts, then they would have high MA and low MTSE. The in-service elementary teachers who had low to moderate MA and high MTSE heavily relied on direct instructional practices with a focus on procedural strategies. Also, these teachers experienced many challenges teaching mathematics in a virtual environment. Findings from this comparative case study have implications for teacher preparation programs, mathematics teaching professional development for in-service elementary teachers transitioning virtual mathematics pedagogy, improving mathematics performance for students, and assisting educational stakeholders in improving mathematics instruction. [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/en-US/products/dissertations/individuals.shtml.]