Using Danish administrative data linked to two independent, validated postpartum depression screenings, we study how postpartum mental health shocks shape women’s labor market trajectories. Event-study estimates show no pre-birth differences in trends between depressed and non-depressed mothers, but persistent employment gaps that widen immediately after birth. Health-care utilization patterns indicate that these differences reflect acute mental health shocks rather than pre-existing trends. The penalties are concentrated among less educated mothers and those in less family-friendly jobs. Our results highlight postpartum depression as a meaningful and unequal contributor to the motherhood penalty.