In the early 2020s the world’s transition from carbon-intensive to climate-neutral energy use has already become a discernible and a difficult-to-reverse process. With Joe Biden’s election as US president, the United States have returned to the Paris Climate Agreement and have become a key driver of this process (along with the EU and China). As a result, the international community has reached a consensus on the ongoing energy transition. This process will require considerable effort and may take several decades. Nevertheless, the impact of energy transition on traditional approaches to energy security, which emerged largely as a result of the global oil crises of the 1970s and 1980s and are centered around the supply of fossil fuels, is already a relevant research topic. This problem is examined relying on the relevant terminological, theoretical and factual material. The article concludes that energy transition will ultimately undermine the carbon paradigm that has underpinned energy security policies since the 1970s. Rapid development of renewable and other low-carbon energy sources will certainly remove key energy security risks of energy importers and, possibly, allow them to achieve energy independence. However, a post-carbon era may also generate new risks. For countries that rely heavily on oil, gas and coal exports, energy transition will result in the loss of markets and revenues. It may present an energy security threat for them as well as it will require a costly and technologically complex process of the energy sector decarbonization. Some exporters, especially those with high fuel rents and insufficient financial reserves, may face serious economic and social upheavals as a result of energy transition. The EU and the US energy transition policies reflect provisions of all three fundamental international relations theoretical paradigms, including realism. This means that the EU and the US policy, aimed at promoting climate agenda, may be expected to be rather tough and aggressive. China as the third key player in energy transition is still following a liberal course; however, it may change in the future.