Most foreign or second (L2) language teaching happens in classrooms where teachers and learners share the same first language (L1), and there has been a long-standing controversy over using L1 in language teaching classrooms. Thus, the present study sought to explore English learners' perceptions about using their L1 in English as a foreign language (EFL) classrooms. The study further aimed to investigate whether English proficiency level had any effect on learners' preferences of using L1 in English classrooms. A total of 75 EFL learners enrolled in an English preparatory program at a foundation university in Ankara voluntarily participated in the study. Data were collected using a questionnaire to determine participants' views on using their L1 in English classes. The results revealed that EFL learners supported the use of English as the only medium of instruction in EFL classrooms and English proficiency level had an effect on learners' preferences of using L1. Findings also indicated that learners with a low level of English proficiency had more positive opinions about using L1 in EFL classrooms as opposed to learners with a high level of English proficiency. On the other hand, regardless of the proficiency level, all participants agreed that they might use their L1 in the class if they really needed to do so. Another significant finding of the study was that learners' willingness to use L1 in the classroom decreased as their English proficiency level increased. In line with these findings, further recommendations were proposed regarding the place of L1 in EFL classrooms.