The debate over the importance of the mother tongue (L1) in EFL classrooms remains unresolved. If some researchers and scholars recognize the role of the mother tongue in teaching and learning English, others do not support the use of L1 for both teachers and students in L2 classes. The goal of this research is to present the results of learners’ use of L1 (Vietnamese) in English-speaking classes. Classroom observation and a semi-structured interview were designed to be delivered to participants for the study, 45 EFL learners at the basic and intermediate levels of an English language center in Can Tho city, and six of them were invited to attend the interview based on convenience sampling. The study’s findings indicated that L1 use was also discovered to be preferred for the following purposes: comprehending teachers’ lessons, expressing ideas or responses, translating English words or sentences, interpreting teachers’ questions or utterances, building rapport by making jokes, reminding mistakes made by teachers, doing pair work or group work, and chatting with classmates. The results also revealed that Vietnamese can help EFL learners make positive changes in their L2 learning journey.