Demographic trends in Korea indicate that the student population is becoming more diverse with regards to culture, ethnicity and language. These changes have implications for science classrooms where inquiry-based, student-centered activities require culturally and linguistically diverse (CLD) students to connect with their peers and successfully navigate both everyday and content specific language. This study introduces the K-TASILT (Korean Teachers’ Attitudes and Self-efficacy for Inquiry and Language based Teaching) questionnaire, which we designed to investigate Korean teachers’ conceptions of diversity, inquiry teaching, and language education to help explore attitudes and self-efficacy towards teaching inquiry and language skills to CLD students. An analysis of 144 primary and secondary schools teachers’ responses revealed that they have fairly positive attitudes towards CLD students and positive self-efficacy for teaching inquiry, but they also have limited self-efficacy for implementing effective language teaching supports for using inquiry teaching with CLD students. We raise questions about the ways in which teachers’ attitudes and beliefs about inquiry teaching and language acquisition could shape teaching practices that limit or afford opportunities for CLD students to participate in school science. We offer implications for science teacher education programs in Korea focused on enhancing diversity and content specific strategies for supporting language learning.