Two main opposing approaches exist regarding the impact of first-language (L1) use in the teaching and learning of English as a foreign language: the monolingual and bilingual approaches. Some linguists assume that students' L1 should be banished from their English classes, whereas others assert that it facilitates the process of learning a target language. The purpose of this study was to investigate learners' attitudes towards the use of L1 in their English classes, both by the students themselves and by their teachers. The current study also determined which factors caused the learners to switch from the TL to their L1. This study was conducted at Salahaddin University, Erbil, at the end of the first semester of the 2016-2017 academic year. It employed a mixed-method approach of data collection and analysis. Two hundred and fifty-eight EFL learners participated in the quantitative data collection, by completing a questionnaire and the qualitative data were collected via face-to-face semi structured interviews with eight EFL learners. The findings revealed that participants had a slightly positive attitude towards the use of their L1 in the facilitation of their TL learning. By referring to current theories of TL acquisition and reviewing recent literature, it can be inferred that learners' L1 has a necessary and facilitating role in acquiring a foreign language under certain conditions.