The ongoing Covid19 pandemic is producing dramatic effects on the economic and social life of many countries, which in turn may further undermine people’s health and well-being. This note focuses on some potential effects on the achievement of the UN Sustainable Development Goal 2 ‘Zero Hunger’ (Target 2.1) and, specifically, on the prevalence of undernourishment. After discussing the main changes induced by the Covid19 outbreak in various dimensions of food security, as identified by the preliminary literature on the topic, the note presents the dynamic estimates (GMM) of the recent determinants of food security, measured through the prevalence of undernourishment (SDG indicator 2.1.1), using a sample of 84 developing countries observed over the period 2000–2017. Since the rate of economic growth turns out to be a relevant determinant, the analysis quantifies the potential consequences that the economic downturn caused by the pandemic may have on the short- and long-run achievements of SDG 2 if proper counterbalancing measures will not be implemented. Such consequences in the short run would consist of millions of new undernourished people, while in the long run the progress made towards the ‘Zero Hunger’ goal are at risk of being completely reversed in the majority of countries. The note concludes by suggesting some directions for future research.