In response to the launch of the OECD "Adaptation Marker" in 2010 and the first complete Creditor Reporting System dataset published in March 2012, this paper examines the credibility of the marker. Our assessment reveals that far less projects than the donor countries reported are in fact relevant to what can be considered climate change adaptation. In brief, we find that roughly 65 % of all activities listed in the original OECD dataset are unrelated to adaptation or at least do not state adaptation as principal or significant objective. Further, from the remaining 35 % only about half of the projects are coded correctly while most of the remaining activities are over-coded. Through this analysis the paper highlights that the current reporting system is prone to overestimation due to several significant insufficiencies. To make the data more reliable and the marker more credible, the OECD as well as the donor countries should work towards indispensable improvements of the guidance for applying the marker.