Women who study or work in male-dominated fields such as science can be targeted by or witness to subtle gender stereotyping, including having their contributions and ideas in science be questioned, discounted, or ignored by others. In this talk I present research examining the detrimental effects of simply witnessing the negative treatment of women in science settings among female science majors. Results of laboratory research showed that, compared to a control group, women in science majors who were exposed to this negative treatment of another woman showed patterns of attribution that support gender stereotypes. Engaging in this stereotypic attribution bias predicted a lower sense of belonging in science and diminished intentions to remain in science post-graduation. This research highlights the need to support science settings that are perceived as welcoming to women, in order to retain women in science fields.