This in-practice article reports a case study investigating the trajectory of teachers who engaged in a professional learning community (PLC) project that aimed to develop language assessment literacy. This case study attempted to examine the following key research question: what changes did the teachers experience in their assessment beliefs and practices during the project? Six out of twenty-five English teachers of secondary education in Indonesia involved in the project were interviewed and observed to understand their regular assessment practices, the challenges or constraints they encountered, their attitudes towards the project and any changes they made during the project. Two main changes in beliefs and practices of assessment literacy and authentic assessment emerged. Findings show that the PLC broadened teachers' understandings of assessment literacy and the use of authentic assessment in practice.