This study applied the psychology of working theory to examine how ambivalent sexism predicts perceptions of decent work and occupational engagement via work volition and career adaptability among female science, technology, engineering, and mathematics (STEM) university students in South Korea (N = 397). Results showed good fit for the measurement and structural models. Hostile sexism negatively affected work volition, which mediated its relationships with decent work and occupational engagement. Work volition and career adaptability jointly mediated the relationship between hostile sexism and occupational engagement. Unexpectedly, benevolent sexism was positively associated with both outcomes, suggesting suppression effects. These findings highlight the complex ways sexism constrains women’s career development while underscoring the importance of supporting women’s agency, pursuit of decent work, and sustained engagement in STEM. Future research should examine broader psychological and contextual variables that may interact with psychology of working theory (PWT) constructs to shape female STEM students’ long-term engagement and access to decent work.