The use of code switching in ESL classrooms is found to be common in Malaysia. This has raised some issues in regard to pupils' exposure to the target language which is the English language. Most English language teachers in the national primary school (SK) in Malaysia have been using code switching or Bahasa Melayu (BM) during English lessons. The aim of this study is to investigate English language teachers’ code switching in the primary ESL classroom. This study focuses on examining the patterns which includes the functions and frequency of code switching by five English language teachers. Using a qualitative case study design, the data were collected using voice recording and semi-structured interviews. Results of the study shows that teachers use code switching in the ESL classroom to a varied extent. Teachers also used code switching in the ESL classroom for six functions which are (1) giving instructions, (2) classroom management, (3) checking understanding, (4) explaining meaning, (5) translating words and sentences and (6) general use. Findings from the interview sessions indicate that teachers agreed that the six functions of code switching are beneficial and helpful resources in facilitating the teaching and learning process, as it ensured the students had more access to the curriculum and knowledge. However, it is essential to recognize that the excessive use of code switching is not advisable in the ESL classroom. Ultimately, teaching and learning should prioritize the English language.