The changing and growing student population in the U.S. demands well-equipped and trained teachers who have the adequate preparation and pedagogical tools to fully meet their diverse needs. This research study examined the perceptions of teachers' preparedness and their efficacy beliefs for teaching English Language Learners. A mixed-method was carried out to address four research questions: 1) What perceptions are held by in-service teachers about teaching practices for ELLs? 2) What is the relationship, if any, between teacher knowledge about teaching ELL students and the instructional practices employed by teachers when instructing ELL students? 3) How effective do in-service teachers feel in teaching ELL students? 4) What factors influence teachers' perceptions of self-efficacy about teaching ELL students? Over 144 teachers participated in the survey questionnaire along with five teachers who participated in focus-groups, interviews, and classroom observations to identify in-depth analysis on their feelings of perceptions and efficacy beliefs. Results from the quantitative study revealed differences in perception and efficacy beliefs for teachers who are bilingual in a second language, teachers who hold a bilingual/ESL certification, and the route in which teachers receive their certification. Qualitative results included the methodologies and cultural competencies that teachers employed in their classroom for English Language Learners. Additionally, participation in professional development activities was found to have an effect in teachers' instructional decisions for teaching ELLs. [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.]