Code-switching is a common phenomenon in a bilingual or multilingual community. English is applied in Indonesia as a foreign language, this phenomenon occurs because we use the Indonesian language or Bahasa Indonesia sparingly. English is only used during class time and sometimes the teacher and the students switch their language between Bahasa Indonesia and English. This study discusses how this phenomenon happened in the English for Foreign Language (EFL) classroom. This study aims to explore the concept, factors, and functions of code-switching in English for Foreign Language (EFL) classrooms. The method of the study uses a literature review which gathered and reviewed journal articles on code-switching in the EFL classroom. There are eight factors influencing code-switching in the acronym namely SPEAKING; S for setting and scene, P for participants, E for ends, A for act of sequence, K for key, I for instrumentalities, N for norms, and G for genre. Code-switching has several functions in the EFL classroom for quotation function, addressee specification, interjection, reiteration, message qualification, personalization and objectification, accommodation, clarification, showing identity, making social distance, and expressive function.