Outcome-Based Education (OBE) is a widely recognised approach to curriculum reform in higher education. This study investigates the level of understanding of OBE among tertiary teachers of English in Indonesia and explores the challenges that hinder, and the factor that support for the implementation of OBE in their classrooms. A total of 632 English teachers from 31 provinces in Indonesia participated in an online survey that comprised closed- and open-ended questions. The study employed descriptive statistics using SPSS 28 and thematic analysis using NVivo 12 to analyse the data. The findings reveal that most teachers feel confident in their understanding of OBE, but their understanding is not comprehensive. Teachers who implement OBE face significant challenges primarily due to self-related factors, including traditional views of a teacher-centred approach to teaching, heavy workloads, lack of awareness about OBE, and limited commitment and willingness to implement OBE. They also encounter difficulties in developing appropriate learning outcomes, teaching strategies, learning materials, and assessment tools. The strong commitment of university leaders is considered the most crucial factor for the success of OBE implementation. This article concludes with implications and recommendations for university leaders, government officials, curriculum developers and future researchers.