Self-assessments are instructional tools with the potential to enhance self-regulatory and language-learning processes in students in the writing classroom. Although widely studied in the first language context, self-assessment research in L2 writing contexts is relatively unexplored. Yet recent research indicates that the demands of writing in a second language can be mitigated when teachers take the time to cultivate self-regulation and metacognition in their students. This positions self-assessment uniquely in the primary L2 writing classroom because it serves to promote self-regulatory and metacognitive skills in learners. In this article, we attempt to clarify major issues in self-assessments in L2 writing settings by first presenting a theoretical construct that underpins self-assessment in the L2 classroom. We then highlight research-informed principles to guide self-assessment in L2 primary settings, offer suggestions on how to incorporate self-assessment into the various stages of writing, and examine challenges in self-assessment implementation. Drawing from Vygotsky's theory of scaffolding and research on metacognition and metacognitive instruction, this article delineates a clear connection between the teaching and learning of this assessment tool and provides examples from a variety of second language contexts. Ultimately, this article serves to inform teachers about how to use self-assessment in their classrooms to promote learner autonomy and independence in learning.