The prevalence of unfounded beliefs (e.g., supernatural or conspiracy beliefs) remains an important issue due to their negative consequences in various domains. Interventions were shown to reduce supernatural beliefs only when addressing pseudoscientific ones. Based on these findings, we designed a single session intervention aiming to teach participants the epistemological distinction between science and pseudoscience. We then assessed the effectiveness of this intervention. Secondary school teachers (N = 130) were assigned to one of two groups focusing on critical thinking with or without the intervention content related to pseudoscience. Supernatural beliefs, conspiracy mentality, and pattern perception were measured using computerized surveys pre- and one moth post-intervention. Mixed-model analyses revealed the expected decrease in conspiracy mentality, d = 0.60, supernatural beliefs, d = 1.01 and illusory pattern perception, d = 0.34 among teachers in the pseudoscience-focused group. Our intervention constitutes a novel cost-effective tool for critical thinking promotion among education professionals.