Pathogenic beliefs are maladaptive cognitive schema that may obstruct a person's ability to achieve meaningful goals in their life. This study sought to revise a previously existing measure of pathogenic beliefs (the Pathogenic Beliefs Scale) by improving the quality of items and separating the ratings of the presence of a pathogenic belief from the distress associated with it. In Study 1 (n = 272), we used item-response theory to identify 21 items from an initial pool of 44 items. In Study 2 (n = 422), we tested the items from Study 1 using confirmatory factor analysis. Study 3 used the combined samples from Study 1 and Study 2 (total n = 528) to compare the revised measure to the Experiences in Close Relationships and the Measure of Parental Style. Results indicate that the revised 21-item PBS has good reliability and convergent validity with related measures, consistent with previous studies of the longer version of the PBS. The 21-item revised PBS is included as supplemental material, and freely available to clinicians and researchers.