Along with the global trend and internationalization, English acts as a supporting tool of connecting the world across the border. English has been attached its importance in Vietnam since the launch of National Foreign Language Project 2020.The innovation in language teaching, learning and assessment in English for specific purposes, accordingly, is seen in some Vietnamese universities. While summative assessment is still a dominant type of assessment, formative assessment has not been captured a sufficient attention. This study is to investigate teachers’ perceptions and practices of FA in ESP class.The challenges faced by teachers in implementing FA will be also uncovered in the study. This may help to provide meaningful suggestions for teachers, course designers and policy makers to help the successful implementation of FA in ESP