The transition to parenthood is accompanied by declined self-esteem levels, which may be explained by parents’ relationship satisfaction. However, prior research examined self-esteem only shortly before and after childbirth and had no or only unmatched childless respondents as a control group, limiting the possibility to examine long-term adaptive processes and the causal interpretation of the associations. Thus, we used panel data (10 years, 4,075 individuals, and 16,122 observations) to compare self-esteem and relationship satisfaction trajectories of parents with matched childless respondents using propensity score matching. We found a quadratic trajectory for parents’ self-esteem, which declined and increased before birth and declined and returned to baseline levels after birth. In contrast, matched childless respondents’ self-esteem decreased linearly before childbirth and then recovered. The quadratic postpartum process in parents was significantly associated with reduced relationship satisfaction. Thus, a fulfilling relationship may help to maintain the positive effects of childbirth on self-esteem in parents.