The purpose of this qualitative embedded multiple case study was to explore the teaching strategies, skills, and knowledge received from English language learner professional development (ELLPD) trainings and seminars and how the application of ELLPD content affected communication with English language learners in the mainstream classroom. The research questions sought to reveal the benefits of professional development training and seminars for English language learner achievement, intervention strategies introduced during the trainings and seminars, and changes in teacher and leader communication with English language learners after the trainings and seminars. Participants were 15 mainstream educators instructing ninth through twelfth graders in mainstream classrooms. The use of Creswell's six steps in research and tiered data collection helped reveal five themes from the exhaustive data processing of five questions included in an educator questionnaire, eight question interview, document analysis of lesson plans, and observation of 11 ELLPD sessions. The findings from the interview triangulated with findings from the document analysis and ELLPD trainings and sessions. Findings showed that educators receiving hands-on training and opportunity to model teaching strategies, knowledge, and skills in ELLPD retained strategies, knowledge, and skills to implement in the mainstream classroom. Implementation of ELLPD as described in the study has potential to improve communication between mainstream educators and English language learners by decreasing barriers between the two stakeholders. [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.]