Discrimination targeting lesbian, gay, bisexual, and transgender (LGBT) students on college campuses occurs. Bystander intervention is important in supporting targeted students and improving campus climate for LGBT students. Peer-familiarity context (i.e., who the bystander knows in the situation) can play a role in bystander intervention, but researchers have not explored the nature of bystander intervention in specific peer-familiarity contexts concerning LGBT discrimination. Using hypothetical vignettes, we examine heterosexual students’ (n = 1616) intention to intervene across 4 peer-familiarity contexts, namely, when the bystander knows no one, only witnesses or targets, only perpetrator, or everyone. We explore the role of student inputs (sociodemographics, self-esteem, attitudes toward LGBT people and political ideology) and experiences (LGBT social contacts, LGBT and social justice course content, and perceived and experienced campus climate) on their intentions to intervene in these contexts. Multiple regression results suggest that across all peer-familiarity contexts, being older, having higher self-esteem, having LGBT friends, taking courses with social justice content, and affirming attitudes toward LGBT people were independently associated with higher intentions to intervene. Males were more likely than females to intervene when they knew no one, while females were more likely to intervene in all other contexts. Race/ethnicity, religious affiliation, witnessing heterosexist harassment, perceptions of campus climate for LGBT students, and student standing were significant in particular peer contexts. Recommendations to promote bystander intervention and future research are presented.