Using Danish registry data, we study how managers’ gender attitudes shape gender inequality in the workplace by exploiting the birth of a daughter – as opposed to a son – as a plausibly exogenous shock to male managers’ gender attitudes. Comparing within-firm changes in women’s labor outcomes depending on the gender of the manager’s newborn child, we find that women’s relative earnings and employment increase by 4.4% and 2.9% respectively following the birth of the manager’s first daughter. These effects are driven by an increase in managers’ propensity to substitute male hires with female hires that have comparable education, hours worked, and earnings. Consistent with this substitution channel, we do not detect any significant effect on firm performance. Because these effects emerge rapidly and persist over time, we can rule out the need for prolonged exposure to gender issues or for personal incentives tied to improving conditions for their own daughters as prerequisites for managers to promote gender equality within their firms.