This study investigates the teachers’ perspective, the implementation process, and the effects of the Merdeka curriculum on promoting multilingualism in ELT classrooms in Indonesia. This study utilized a qualitative research design, explicitly a case study approach. This study has two samples selected through purposeful sampling by the researchers. The research employs in-depth interviews, field notes, and documentation as its primary instruments. This study demonstrated that adopting the Merdeka curriculum was transformative and empowering, as evidenced by participants’ experiences and prior knowledge. The perception of the Merdeka curriculum implementation was based on various factors such as content, differences, reactions, expectations, advantages, disadvantages, supports, and hindrances. In supporting multilingualism, the process in the school began with the principal’s initiation, followed by training to comprehend the curriculum. Subsequently, each set of materials was developed, and the learning and assessment principles were implemented to achieve the Pancasila student profiles. As a result of this curriculum, teachers have become more flexible and put in more effort to cater to students’ preferences. After that, students exhibit heightened confidence, ingenuity, and engagement in the learning process, so availing themselves of increased opportunities for self-exploration. Through implementing the Merdeka curriculum, the promotion of multilingualism in the classroom has many advantages, including enhancing the well-being of students, encouraging intercultural perspectives within the classroom, and placing value on all languages in the classroom.