In male-dominated STEM fields, workplace culture is often cited as a factor for women’s attrition. In the present research, we used longitudinal field data to examine how changes in the perceived normative support for gender-inclusive policies and practices over 6 months relate to changes in women’s and men’s experiences of fit and commitment to their organization. Longitudinal analyses of survey data from a sample of 181 engineers revealed that increased perceptions of support for gender-inclusive policies and practices predicted increased organizational commitment only among women, an effect that was mediated by an increase in organizational value fit. Additional analyses suggest that perceptions of change in normative attitudes toward inclusive policies were more predictive of women’s organizational commitment than the awareness that the policies were in place or that one has personally benefitted from them. The implications of an inclusive workplace culture for supporting women’s retention in STEM are discussed.