This paper studies the relative labor market outcomes of grandmothers in comparisonto grandfathers before and after the arrival of the first grandchild using Danish ad-ministrative data and an event study approach. We find that women’s labor marketoutcomes decline at a steeper rate than men’s after the arrival of the first grandchild.We find gender gaps in earnings of three and nine percent five and ten years after thearrival of the first grandchild, which is almost exclusively driven by women’s reductionsin full-time employment. We document that these "grandchild penalties" are larger inperiods with more generous retirement options.