Given the persistent underrepresentation of women in leadership positions, there is growing attention towards men’s roles as allies for gender equality. As individuals who are overrepresented in positions of power and influence, men’s support and advocacy towards women can positively impact women’s advancement in organizations. To test this claim, we integrate the resources and power literatures to examine how male allies can support women’s leadership development. We theorize that men's allyship can support women’s work resources, and thus, foster their leadership. In our mixed-method research with working women, we used a recall study (N = 52) and a two-wave study over one year (N = 222) to triangulate results. We found that men’s allyship supports women’s resource acquisition (e.g., providing developmental opportunities) and prevents resource loss (e.g., interrupting sexist incidents). Overall, we aim to empower he for her development by informing theory and practice on how men’s allyship can increase women’s representation in leadership.