The securitization process, first identified and analyzed by the School of Copenhagen, has received growing attention among critical security studies scholars over time. First defined as a speech act, it has gradually been understood in a sociological perspective which requires additional methods other than discourse analysis. However, other methods are not systematically employed and barely discussed as far as, on the one hand, their relevance and, on the other hand, their implementation are concerned. For instance, ethnographic approaches have been mentioned as an option to study micro practices of securitization. Yet, even if a few studies actually implement ethnographic methods – such as participant observation – to explore securitization processes, the methodological procedures and “tricks” are not fully detailed. This paper aims at filling this gap. It explores the method of participant observation applied to the study of securitization. Taking the case of environmental securitization within the United Nations, this paper proposes to explain the relevance of participant observation to analyze securitization – why to use it – but also to describe the different steps and procedures of this method – how to use it. Based on this case-study, this paper also seeks to contribute to a broader reflection on the implementation of methods relevant to security studies and IR en general.