Many high school science teachers feel ill-equipped and ill-trained to adequately support the ever-increasing number of ESL/EFL students. The purpose of this qualitative single case study was to explore science teachers' perspectives of effective science teaching strategies, the challenges implementing science teaching strategies, and suggestions for improving science teaching for ESL/EFL students. The central research question was: What are science teachers' perspectives of effective science teaching strategies, challenges implementing science teaching strategies, and suggestions for implementing science teaching strategies for helping ESL/EFL students? The sub-questions were: (a) How do science teachers perceive the effectiveness of science teaching strategies for ESL/EFL students? (b) Why do science teachers believe that those science teaching strategies are effective for ESL/EFL students? (c) What challenges do science teachers have when implementing science teaching strategies in teaching EFL/ESL students? (d) What suggestions do science teachers have for implementing science teaching strategies for teaching EFL/ESL students? Interview data were collected from 11 science teachers through Zoom. Science teachers' lessons plans, homework assignments, projects, and assessments were also collected. The results showed the following significant themes: (1) Technology is useful; (2) teacher demonstration and hands-on activities are helpful; (3) comprehension strategies help; (4) vocabularies building strategies are needed; (5) asking questions help clarify the concept; (6) science teaching strategies are diverse; (7) Both advantages and disadvantages exist; and (8) top challenges involved time constraint, motivation, and insufficient funding. Teachers' suggestions were described. Recommendations for educational leaders, teachers, and researchers were included. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]