In many educational contexts, L2 writing assessment tends to emphasize its summative functions (i.e., assessment of learning--AoL) more than its formative potential (i.e., assessment for--AfL). While the teacher plays a dominant role in AoL, central to AfL is the role of the students, alongside that of the teacher and peers. A student-centred approach to L2 writing assessment involves learners actively in setting goals, monitoring their progress, and deciding how to address the gaps in their learning. Such a focus, also referred to as assessment as learning (AaL), puts students at the centre of classroom assessment. In the L2 writing literature, however, descriptions and explanations about how AaL can be implemented in the writing classroom are scant. This article attempts to provide a clear understanding of AaL and how a student-centred approach to classroom assessment can be applied in the L2 writing classroom, thus contributing new knowledge to the existing literature on classroom L2 writing assessment.