Does fathers’ leave, a policy intervention that disrupts traditional gender roles, promote more gender-equitable attitudes? We examine this question by studying a policy reform in Estonia that tripled the length of fathers’ leave for children born on or after July 1, 2020. The reform promoted fathers as care givers – it offered both parents the opportunity to conceive of their social roles in a less traditional fashion and to thereby reassess traditional beliefs about the appropriate roles and essential traits of men and women. Using an innovative design, we combine this natural experiment with a unique survey of new parents whose children were born in the six months before (N = 614) and after (N = 748) the reform. The reform led to a sizeable rise in gender-egalitarian views in the economic, social, and political domains among both mothers and fathers. Support for positive action policies, which promote women at the expense of men, only increased among mothers but not fathers. We also examine the response of the general public to the reform, based on an informational, indirect treatment (in contrast to direct exposure of new parents) and find no effects. These results show that direct exposure to progressive social policy has the power to weaken patriarchal attitudes, a finding that is of considerable practical relevance given the continued prevalence of attitudinal gender bias even in developed democracies.