Protecting the environment and the Earth's natural resources is one of the most important tasks for modern societies, economies, and countries. Changes in the environment have made climate protection a key task of state policy implemented at the local, national, and international. They also have caused such negative social manifestations as environmental radicalism and terrorism. The purpose of this paper was to analyze the capacity of state institutions to prevent environmental terrorism and radicalism, particularly in the Russian context, by identifying and prioritizing key challenges and countermeasures. A mixed-methods approach was adopted, involving both qualitative and quantitative analyses. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a total of 35 articles and reviews were selected to provide a foundation for understanding eco-terrorism trends. Additionally, an expert survey was conducted with 44 qualified participants to rank problems and recommended actions. The Kendall concordance coefficient was used to assess the consistency of expert opinions. The authors conclude that low environmental awareness and insufficient cooperation between state institutions and environmental organizations are the most significant challenges in preventing eco-terrorism. To adequately and competently prevent environmental terrorism and radicalism in society, the prevention system must be based on clear and thoughtful actions by state institutions.