The transition to parenthood is a period of new adjustments for couples and may pose a risk of relationship deterioration. During this early child-rearing, father’s involvement in housework and care activities could reduce parental stress. To encourage father’s participation in the private sphere, Nordic countries have pioneered father’s quota leave. The leave benefits are inclusive for all, yet fathers’ leave uptake remains socially uneven. Our study examines the overall and heterogeneous effects of the 2013 Finnish leave reform on the risk of couples’ separation, considering educational disparities in leave uptake and separation risk. We used Finnish register data, natural experimental design and event history analysis to assess separation risk among 34,689 different-sex couples who had their first child together. Our findings show that couples who became parents after the reform experienced about 7 percentage points lower risk of separation than pre-reform couples. The decline was particularly pronounced (about 13 percentage points) among lower-educated couples, who increased their leave-taking more than others.