Teachers play a crucial role in the implementation of an English as a lingua franca (ELF) perspective in the classroom. However, little research has been conducted on what challenges teachers might encounter and what types of support are needed to teach English from an ELF perspective. This study thus explores the experiences of seven primary teachers enrolled in a teacher development programme designed to support their attempts to teach from an ELF perspective in South Korea. Drawing on in-depth interview data, the paper provides detailed accounts of the challenges and strategies for developing ELF-aware teachers. The main challenges encountered included a lack of the pedagogical skills required to implement planned lessons, the paucity of relevant instructional materials, and parents' strong preference for Standard English. It is possible, however, that these challenges could be addressed by creating opportunities for guided reflection, peer collaboration, and effective communication. Implications for future ELF-aware teacher development programmes are also discussed.