This research experimentally examined the effects of exposure to intergroup conspiracy theories on prejudice and discrimination. Study 1 (N = 166) demonstrated that exposure to conspiracy theories concerning immigrants to Britain from the European Union (vs. anti‐conspiracy material or a control) exacerbated prejudice towards this group. Study 2 (N = 173) found the same effect in a different intergroup context – exposure to conspiracy theories about Jewish people (vs. anti‐conspiracy material or a control) increased prejudice towards this group and reduced participants’ willingness to vote for a Jewish political candidate. Finally, Study 3 (N = 114) demonstrated that exposure to conspiracy theories about Jewish people not only increased prejudice towards this group but was indirectly associated with increased prejudice towards a number of secondary outgroups (e.g., Asians, Arabs, Americans, Irish, Australians). The current research suggests that conspiracy theories may have potentially damaging and widespread consequences for intergroup relations.