The main aim of the present paper is to provide an in-depth look at the relationship between English and Algerian Arabic (L1) in an EFL classroom in the department of English at Tlemcen University, Algeria. In this regard, the researchers try to determine the reasons and functions behind the use of Code-Switching among EFL teachers and students of English to Algerian Arabic. To conduct this research work, the researchers collected data through an interview that was conducted with 16 teachers of Comprehension and Oral Expression, Literature, and Civilization in the Department of English at Tlemcen University in Algeria, and supported by a classroom observation of students with the same teachers. Findings revealed that the use of Algerian Arabic is inevitable. Teachers' responses exhibit negative attitudes towards English-Algerian Arabic code-switching in class, but they do not deny its integration as a pedagogical necessity to explain difficult words and expressions that are hard to be grasped in the target language. The results also showed that teachers peacefully attempt to get their students accustomed to lectures delivered in English solely by avoiding translation and applying the direct method of TEFL. Furthermore, they declare that infrequent use of AA is beneficial to foster students' academic achievements and language skills development.