This study aims to identify types of code-mixing used by English teachers and to discover the perceptions of the teachers about the use of code-mixing in EFL classrooms. To achieve the goal of this study, the researcher used a qualitative design. The research data were collected through observations and semi-structured interviews with three English teachers at MAS Jeumala Amal in Pidie Jaya, Aceh. The participant was taken by using purposive sampling technique. The observational data were transcribed and categorised based on Muysken's theory (2000), while the interview data were analysed to understand the teachers' perceptions. The findings of this study showed that the types of code-mixing used by the teachers were found in three types: insertion (105), alternation (60), and congruent lexicalization (24). Moreover, teachers viewed the use of code-mixing positively. The teacher considers code-mixing as an effective practice in the EFL classroom. The use of code-mixing reduces students' comprehension constraints, makes students more responsive, and helps students understand the explanations more quickly. The results of this study contribute to strengthening the legitimacy of code-mixing as an effective pedagogical strategy in EFL teaching to improve student comprehension and create an inclusive learning environment.