We know a great deal about the immediate impact of becoming a parent, but less on the more long-term impact as parents are adapting to the rapid developmental changes that characterize the early childhood period. This longitudinal study explored how parental self-esteem and emotion regulation develops during pregnancy, infancy, toddlerhood and preschool-age. We used nine waves of data from 550 Dutch fathers and mothers to examine stability and change in self-esteem and emotion regulation from pregnancy until 4 years postpartum, for both first and later pregnancies. Self-esteem and emotion regulation showed the same trajectory of change, with decreases during pregnancy and infancy, and increases during toddlerhood and preschool-age. Fathers had higher mean-levels of self-esteem and emotion regulation than mothers, but child age-related changes were the same for fathers and mothers. First-time parents and second-, third-, or fourth-time parents did not differ in mean-level self-esteem and emotion regulation, nor in age-related change. Over the course of 4 years postpartum, parents slightly increased in self-esteem and emotion regulation. The results suggest that, for the average parent, the birth of a child causes a temporary deviation from the overall trend toward greater self-esteem and emotion regulation. Since both traits are predictive for parental well-being, positive parenting and child development, future research needs to investigate if an intervention should and could ease the transition to parenthood and thereby prevent this decline.