["Analyses of Social Issues and Public Policy, Volume 26, Issue 1, April 2026. ", "\nAbstract\nDespite the importance of a strong science, technology, engineering, and mathematics (STEM) workforce, the culture of STEM deters many groups, including sexual and gender minorities (SGM) from entering STEM fields (i.e., women, Latino/a, Native American, first‐generation students). Because SGM individuals’ STEM belonging and motivation are believed to follow similar psychological processes to other underrepresented groups in STEM, we examined how expectations for success in STEM, personal endorsement of masculinity/femininity and agency/communion, and the masculine (unfeminine) and agentic (uncommunal) nature of STEM are associated with STEM motivation and belonging depending on participants’ sexual and gender identities. Men expressed greater STEM belonging and motivation than women, and STEM fields were perceived as more masculine and agentic than feminine and communal. Participants’ expectations for success in STEM were positively associated with STEM belonging and motivation. Perceiving agentic and communal opportunities in STEM also positively predicted STEM belonging and motivation. For SGM individuals, perceiving feminine gender expression in STEM was associated with increased STEM belonging and motivation (particularly for SGM women). Implications for addressing the underrepresentation of SGM individuals in STEM are discussed.\n\nPublic Significance Statement\nWhen sexual and gender minorities (SGM; especially SGM women) perceive feminine gender expression and communal opportunities in science, technology, engineering, and mathematics (STEM), they are more likely to express STEM belonging and motivation. Institutions and policymakers may be able to increase the representation of SGM in STEM by supporting and encouraging the expression of femininity and highlighting and providing communal opportunities in STEM.\n"]