We test for gender bias in promotions at financial institutions using two central predictions of Becker’s (1957, 1993) model: firms with bias will (1) raise the promotion bar for marginally promoted female workers, and (2) incur costs from forgoing efficient employment practices. We find support for both of these predictions using a new nationwide panel of mortgage loan officers and their managers encompassing approximately 72,000 workers from over 1,000 shadow banks from 2014 to 2019. Overall, our findings provide evidence that gender bias is an important factor in gender gaps at financial institutions.