"That's so gay," a popular expression on campuses, is a sexual orientation microaggression that can contribute to a hostile environment for lesbian, gay, and bisexual (LGB) students. Using data from a campus climate survey conducted at a large urban university, we investigated use of the phrase among heterosexual male undergraduates who are emerging adults (18-25 years). Multiple regression analysis suggested that saying the phrase is positively associated with hearing peers say it and with holding negative perceptions of feminine men, whereas having LGB acquaintances was negatively associated with use of this expression. We offer practice and policy recommendations for curbing its use, thereby enhancing campus climate.