This qualitative study was conducted to explore non-native EFL teachers' knowledge base performed during instruction, perceived knowledge base underlying teaching practices, and perceived pathways of knowledge base construction. The data from four sources including video recordings of classroom observations, interviews, detailed field-notes taken during classroom observations, and participants' reflections revealed that the eight participants integrated knowledge of the English language, other content areas, instructional delivery, classroom management, and the changing world and social contexts in their instruction. The findings indicated that the participants realized that their knowledge consisted of language construction and skills, other content areas, ability to teach, understanding students' strengths, weaknesses, and needs, the changing world, social contexts, and technology, as well as problem solving ability. Also, they perceived teacher education programs, additional learning experience, teaching experience, in-service professional development activities, and a working environment as key sources of knowledge base construction for non-native teachers.