Our actions towards an outgroup are motivated not only by our perceptions, but also by how they think the outgroup perceives the ingroup (i.e., meta-perceptions). To determine the strength and accuracy of negative meta-perceptions, we compared actual perceptions of representative Democrats and Republicans (N = 1056) to meta-perceptions each group inferred (Study 1). Next, to determine the consequences of negative meta-perceptions, we used a 2-wave study (N = 2707) to determine how strongly meta-perceptions are associated with outcomes assessed months later (Study 2). We find that both groups think the other party expresses prejudice and dehumanization towards their party that are 50-300% larger than actual levels of prejudice and dehumanization. We also find that these misperceptions are independently associated with desired social distancing from the other party and willingness to harm the other party at the expense of the country. This research shows that partisan meta-perceptions are subject to a strong negativity bias, with Democrats and Republicans agreeing that meta-perceptions of partisanship are much larger than reality, which fosters intergroup hostility on both sides.