Of the English Language Learners (ELLs) in USA K-12 schools, 665,000 are identified as having a disability. In mathematics, ELLs with disabilities have significantly lower outcomes than English dominant, and non-disabled peers. Numerous studies over four decades have linked student outcomes to teacher self-efficacy (i.e. belief in ability to perform a task for expected outcomes). Considering many ELLs with disabilities receive mathematics instruction from special education teachers, there are questions about the self-efficacy of these teachers to provide quality instruction, since there are few studies focused specifically on preparing or supporting special education teachers to teach mathematics to ELLs with disabilities. The purpose of this dissertation is to examine in-service special education teachers' overall self-efficacy in teaching mathematics in teaching any student with a disability and in teaching ELLs with disabilities in culturally and linguistically responsive ways. One hundred seventeen special education teachers from 9 states were recruited for this study which utilized surveys and follow up interviews. Six participants, chosen for having low or high self efficacy in teaching mathematics to any student with a disability or in teaching mathematics to ELLs with disabilities, were interviewed about factors which were helpful or harmful to their self-efficacy. Themes from the data included (a) teacher preparedness, (b) student characteristics, (c) teaching pedagogy, (d) building culture, (e) overall teacher disposition and (f) culturally responsive pedagogy.