This article explores how Canadian youth who participate in Gay-Straight Alliances (GSA) and teachers who advise them perceive and/or experience bi/pansexuality. Participants’ perspectives on, definitions of, and alignment with bi/pansexuality are examined as they unpack mis/understandings associated with nonmonosexual identities. For GSA members, bisexual and pansexual identity labels were not interchangeable terms; bisexuality was associated with the fe/male binary and pansexuality served as a personal contestation to this dichotomy. Despite these distinctions, both nonmonosexualities were marked by invisibility, mis/understandings, and prejudice in school. Findings emphasize how students’ knowledge of sexual diversity and fluidity was more nuanced than their GSA advisors due to personal online research. GSA participation enabled bi/pansexual knowledge exchange among students and teachers, and promoted overall understandings of bi/pansexualities. Although GSA involvement facilitated opportunities to discuss bi/pansexualities, this article also highlights how an effort should be made to integrate bi/pansexual content in these clubs.