Political polarization between conservatives and liberals threatens democratic societies. Ameliorating liberal research participants’ negative feelings, evaluations, and stereotypes towards conservatives might be one step into the direction of a political depolarization. In a sample of U.S.-American liberal research participants recruited via Amazon’s Mechanical Turk (N = 271), we randomly assigned participants in a pre-post-design either to a clinical-psychological, metacognitive-intervention (MCT), an educational, or a no-treatment-no-pre-measurement-control-condition. In the MCT-condition, participants were first asked seemingly simple questions that frequently elicited incorrect responses, followed by corrective information. In the educational condition, information was conveyed in a simple narrative form. MCT was significantly more effective in ameliorating liberal participants’ negative feelings, evaluations, and stereotypes towards conservatives compared to the other two control-conditions. Further, MCT-participants significantly reduced their negative feelings, negative evaluations, and perceptions of threat from pre- to post-measurement, significantly more than participants in the educational condition. The results of our preliminary study and its implications are discussed, and recommendations for further research are made.