Sexual minority (e.g., gay, lesbian, bisexual) people are 9 times more likely than heterosexual people to be diagnosed with OCD. Cognitive models of OCD posit that obsessive beliefs drive clinical OCD symptoms, however, obsessive beliefs have yet to be examined based on sexual orientation. Due to prior research identifying that sexual minority people are more likely to be diagnosed or treated for OCD and present with unique symptom profiles, elucidating underlying beliefs may partially explain why these disparities persist. Participants (N = 505) completed the Obsessive Beliefs Questionnaire-44 (OBQ-44) upon admission to a partial hospital/residential treatment program for OCD. The three largest sexual orientation groups were bisexual/pansexual (n = 46), gay/lesbian (n = 34), and heterosexual (n = 425). To examine differences, the OBQ-44's subdomains (perfectionism/certainty, responsibility for harm/threat, and importance/control of thoughts) were compared by sexual orientation. Results highlighted that perfectionism/certainty and harm/threat were significantly higher for bi+ compared to heterosexual participants, but not compared to gay/lesbian people, or between heterosexual and gay/lesbian people. This paper adds to a growing body of literature suggesting that the experience of bi+ individuals is different, and future research should identify the role of bi+ discrimination in the development of these core beliefs.