By synthetically producing nitrogen fertilizers from ammonia (NH₃), the Haber–Bosch process has been feeding humanity for more than one hundred years. However, current NH₃ production relies on fossil fuels, and is energy and carbon intensive. This commits humanity to emissions levels not compatible with climate goals and commits agricultural production to fossil fuels dependency. Here, we quantify food and energy implications of transitioning nitrogen fertilizers to net-zero CO₂ emissions. We find that 1.07 billion people are fed from food produced from imported nitrogen fertilizers. An additional 710 million people are fed from imported natural gas feedstocks used for fertilizers production, meaning that 1.78 billion people per year are fed from imports of either fertilizers or natural gas. These findings highlight the reliance of global food production on trading and fossil fuels, hence its vulnerability to supply and energy shocks. However, alternative routes to achieve net-zero emissions in NH₃ production exist, which are based on carbon capture and storage, electrification, and biomass. These routes comply with climate targets while mitigating the risks associated with food security. Yet, they require more land, energy, and water than business-as-usual production, exacerbating land and water scarcity and the use of limited natural resources. Transitioning fertilizers to net-zero emissions can contribute to climate and food security goals, although water, land, and energy trade-offs should be considered.