Science, technology, engineering, and math (STEM) stereotypic attribution bias (SSAB) is the tendency to spontaneously generate external attributions for men’s setbacks in STEM fields and to spontaneously make internal attributions for women’s setbacks in STEM fields. Among samples of undergraduate STEM students, STEM settings perceived as unwelcoming to women through self-report (Study 1) and a manipulation (Study 2) were shown to predict SSAB. Among undergraduate women, experiencing the negative treatment of other women in a science setting predicted SSAB, which was negatively correlated with feelings of belonging in STEM (Study 1) and with intentions to continue in STEM after graduation (Studies 1 and 2). Research materials (i.e., data, measures, materials, etc.) used in both studies will be made available upon request to either of first two authors. The results of our studies suggest that those interested in increasing retention of women in STEM majors should develop strategies designed to reduce internal attributions for women’s setbacks among women facing negative STEM environments and cultivate a more positive climate for women in STEM fields.