In a world barreling down into a worsening climate crisis, negative persuasive attacks to necessary climate policies are major threats to the public's support of governmental mandates to mitigate climate change. To protect against such attacks, here we introduce and investigate the effect and the treatment heterogeneity of the trust inoculation, a psychological inoculation strategy designed around the influence of trust as a key social dimension of persuasion. Across three preregistered studies, in one Swiss state (N = 389), in seven European countries (N = 2805), and in the United States (N = 3586), and in a mega-analysis (N = 6697), we provide evidence that inoculating citizens with the trustworthiness of key energy stakeholders protects citizens' support for renewable energy against multiple negative persuasive attacks (δ = 0.16). Whereas baseline trust in key energy stakeholders did not moderate the effects, the trust inoculation selectively protected the citizens most susceptible to negative persuasive attacks, i.e., participants with high biospheric values. Study 3 showed that the trust inoculation, rather than a simple trust message, is responsible for the protection from incoming persuasive attacks. Our findings demonstrate that the trust inoculation may serve as an easily implementable, and scalable umbrella strategy to engender a modest but significant protection for governmental mandates against multiple negative persuasive attacks.