This paper adds to writing to learn research by reporting on empirical and conceptual studies on the subject matter but also by speculating on the learning virtues that writing offers besides its function as an assessment tool, namely that it can provide students with an adequate avenue to reflect on their learning. For this purpose, I reviewed 17 studies spanning a 17-year period (2004-2020) and representing both the L1 and L2 contexts. Reviewed studies examined writing to learn in different disciplines and grade levels across countries, including the US, Canada, Turkey, Norway, Spain etc. Later in this paper, I set out to elaborate on thematic patterns if these existed and identify areas where further research may be warranted. Findings indicated that writing to learn is an effective instructional strategy across different grade-levels and disciplines both in the L1 and L2 teaching and learning contexts. Finally, this paper overviews relevant pedagogical implications and future research directions.