The idea of sustainable assessment has been embarked upon by many educators since its introduction more than two decades ago. The main aim of sustainable assessment is to equip students for their learning beyond their current study. Past studies have warned that this may not be well taken-up in some contexts where assessment has to assume “double-duty” or even “multiple-duty”, such as those in the Confucius Heritage Cultures (CHCs). Further, the immediate learning objectives of some high-stake examinations system may blindfold and hamstring the goal of sustainable assessment of preparing students for future learning. Clearly, this created much assessment tension (AT) for the teachers. However, the investigation into teachers’ ways of experiencing AT and its relationships with sustainable assessment is not heard of. Using samples from three different profile secondary schools and Ministry of Education (MOE) headquarters in Singapore, semi-structured interviews were used to identify variation in Chinese Language (CL) teachers’ experiences of AT. This phenomenographic study argues that teachers’ conceptions of AT determine the possibility and the extent of the use of sustainable assessment in their teaching. This paper seeks to examine the taking up of sustainable assessment in the context of different ways that AT is experienced and understood by teachers in a CHC. Findings on teachers’ conceptions of AT is presented, and each is discussed for insights into teachers’ meanings and practices of assessment, as well as how they managed the tension. In particular, instances of how sustainable assessment has been taken up are discussed to highlight more productive ways of understanding and using this assessment.