Human Rights Watch (HRW), Amnesty International (Amnesty), and other like-minded organisations have become major actors in the world of international humanitarian law (IHL). Every year they issue hundreds of publications purporting to document violations and to promote IHL enforcement. These publications are ubiquitously cited in the media, and used as source material for governmental and United Nations inquiries, quasi-judicial bodies, the International Criminal Court, academic studies, and other frameworks. Yet, despite the increase in the number, role and influence of non-governmental organisations (NGOs) working on IHL enforcement, conflicts and civilian deaths show no signs of abating. Among the factors that reduce NGO impact in these areas is the demonstrated weakness of these organisations in the realm of fact-finding, and the tension between these activities and emphasis on political advocacy. This article will thus analyse both objective and subjective aspects of NGO fact-finding during armed conflict, including mandates and methodology, selectivity, the application of legal standards, military expertise and sourcing. These issues will be examined through case studies of Amnesty and HRW publications on the conflicts in Yemen, Ukraine and the 2014 Gaza War. The article will conclude with recommendations for NGOs and the actors with which they interact.