As the humanitarian sector reconsiders its purpose and scope, sustainability risks becoming an afterthought, precisely when it is most needed. In this blog, Claudio Alberti (OECD Development Co-operation Directorate), Sofiya Yuvshanova (UNICEF Europe and Central Asia Regional Office), and Samandar Mahmodi (Afghan Evaluation Society) draw on recent evaluations and the OECD DAC criteria to argue that sustainability remains relevant in humanitarian settings when applied flexibly, with attention to systems, ownership, and adaptive pathways.