||In English as a Foreign Language (EFL) classes, it is noticed that teachers and students use sometimes other languages such as a mother tongue (L1) and/or the official language (L2) to make the lesson better understood. Cause (2007) said that this dynamic passage from L3 to L1 and/or L2 in teaching a foreign language is called code switching. Code switching is used by the EFL teachers to make clearer the lesson to the learners, to claim order or discipline in the classroom, to explain the rules, to express a feeling of angry, to make humour and to reformulate the instruction. Benin being itself a multilingual country because of the presence of more than fifty national languages, the usage of mother tongues or the official language in Beninese EFL classes intervenes by taking into account many conditions. First, the geographical area is important in the choice of the L1. Secondly, the L1 of the EFL teacher is not negligible. If the national language used as “lingua franca” in this part of the country is not understood by the students, they make use of the L2 constantly. If in non-linguistic courses code switching’s role is not important, with the linguistic courses it essentially plays a didactic and communicative role in order to solve lexical access difficulties and has a sociolinguistic function in EFL classes. The objective of the present research is to point out the importance of the use of L1 and/or L2 in EFL classes, its advantages and disadvantages. To reach the goal of this investigation, some research instruments such as questionnaire questionnaire, classroom observation, and interview have been used.