This study draws on quasi-experimental data from participants in heterogeneous face-to-face deliberations on sexual minority rights in Poland. It examines whether disagreement perceived during deliberation decreases—as deliberative theorists hope—or rather exacerbates—as psychological research predicts—extreme views. The study also analyzes whether extreme deliberators report that their views were polarized and whether self-reported polarization is greater following deliberations perceived as contentious. Third, the study tests the correspondence between pre- to posttest and self-reported polarization measures. As predicted, extreme deliberators who perceived disagreement polarized on the discussed policies and on issues more generally related to sexual minorities and also reported greater opinion polarization. Validating the self-reported measure with the binary index suggests that deliberators relatively accurately reported polarization.