Objective: Decreased childhood vaccination can lead to local outbreaks of vaccine-preventable disease. In a pilot study from our group, 72% of parents of newborns reported initiating their vaccine decision-making for that child prior to conception. Since a sound understanding of the timing of parental vaccine decision-making is needed to direct educational efforts, we surveyed a national cohort of first-time parents to extend our preliminary findings. Methods: From March 2019 to March 2020, first-time parents of newborns in mother-baby units of the Better Outcomes through Research for Newborns (BORN) network completed the Vaccine Preference Development Survey (VPDS). The VPDS measures intent to vaccinate, timing of vaccine decision-making, and sources of influence. Univariate and multivariate analyses explored associations between intent to vaccinate and timing of vaccine decision-making with demographic variables. Results: Twenty-three sites provided surveys through site-specific nonrandom systemic sampling; 91% (1393/1524) of surveys were used in the analysis. Most parents planned to fully vaccinate (1191/1380, 86.3%) and started vaccine decision-making prior to conception (850/1378, 61.7%). Maternal age, race and ethnicity, relationship status, and education were all significantly associated with planning to fully vaccinate and preconception decision-making (P < .001). Preconception decision-making correlated strongly with intent to fully vaccinate (P < .001). Parents influenced by personal education, medical professionals, and family/friends were more likely to endorse preconception decision-making; those strongly influenced by internet/social media were less likely to allow all vaccines or start decision-making prior to conception. Conclusions: Vaccine decision-making occurs preconception for most new parents. Initiating vaccine discussions during the birth hospitalization may be too late.