US elementary schools and classrooms are settings for gender socialization. Whether intentional or not, teachers communicate expectations for students’ gender identity/expression in their classrooms and beyond; however, teachers’ influences on gender identity/expression remain underexamined. The current study aims to fill gaps in the literature by investigating elementary teachers’ potential contributions to classroom gender climate via a quantitative, quasiexperimental design. Participants for this study were 299 licensed elementary school teachers who were currently practicing in the United States, teaching Kindergarten, first, second, third, fourth, or fifth grade. Participants were recruited directly and indirectly through principal and teacher emails obtained on publicly available lists (e.g., state department of education websites and school websites) and via social media advertising. Participants were randomly shown one of six vignettes describing a target student (either male or female), whose gendered traits, interests, and behaviors were varied such that the student was either gender non-conforming (e.g., a strongly masculine female), gender-conforming, (e.g., a strongly feminine female) or neutral in gender expression. After presentation of the vignette, participants were asked to complete a questionnaire containing their predictions about the target student’s sexual orientation, as well as achievement and capability beliefs in gender-typed academic domains (math, science, reading, and English/language). Participants were then asked to complete a gender climate scale adapted for this research from the work of Ullman (2017) and Brant (2014). Results from the self-reported gender climate scale indicated that the majority of participants held positive, accepting attitudes toward diverse expressions of gender in their classrooms, regardless of demographic factors such as age, relationship status, teaching experience, gender, race/ethnicity, number of children, school sector, or school socioeconomic status. However, fewer participants overall reported high self-efficacy for engaging in instructional activities and design aimed at creating an inclusive gender climate in their classroom. Additionally, many participants felt less capable of identifying bias against students with diverse gender identities in the school setting. Results from vignette predictions, an indirect measure of teachers’ attitudes, revealed positive expectations of all students’ success in traditionally masculine-typed school subjects (math and science). Regardless of gender identity or expression, target students were expected to have moderate success in math and science. Teachers who reported creating more inclusive classroom gender climates also tended to predict higher math and science success for target students. Gender stereotyped attitudes related to sexual orientation and success in traditionally feminine-typed school subjects were apparent, however. Participants perceived gender nonconforming male target students as most likely to have a non-heterosexual orientation. Female target students were assumed more likely to be heterosexual, regardless of gender expression. Additionally, teachers expected target students with feminine gender expressions— regardless of gender identity—to experience more success in reading and English/language than masculine target students. This expectation held regardless of teachers’ self-reported contributions to classroom gender climate. These results suggest that US elementary school teachers may feel positive and accepting of students’ gender diversity while simultaneously feeling less capable of engaging the instructional practices necessary to create inclusive classroom gender climates, including confronting bias. Additionally, elementary teachers may hold gender stereotyped attitudes regarding students’ gender diversity, including the conflation of gender and sexual orientation and the expectation that feminine students will perform better in feminine-typed subjects. Taken together, these findings point to teachers’ potential implicit gender essentialist attitudes that may contribute to restrictive gender climates and marginalizing school experiences faced by students of diverse gender identities. These findings elucidate areas for intervention and teacher training, specifically related to implicit gender bias and specific classroom/instructional practices aimed at fostering inclusive classroom gender climates.