The objectives of this study were to determine if racial and ethnic differences in personal capital during pregnancy exist and to estimate the extent to which any identified racial and ethnic differences in personal capital are related to differences in maternal sociodemographic and acculturation characteristics. Data are from the 2007 Los Angeles Mommy and Baby study (n = 3,716). Personal capital comprised internal resources (self-esteem and mastery) and social resources (partner, social network, and neighborhood support) during pregnancy. The relationships between race/ethnicity and personal capital were assessed using multivariable generalized linear models, examining the impact of sociodemographic and acculturation factors on these relationships. Significant racial and ethnic disparities in personal capital during pregnancy exist. However, socioeconomic status (i.e., income and education) and marital status completely explained Black-White disparities and Hispanic-White disparities in personal capital, whereas acculturation factors, especially nativity and language spoken at home, partially mediated the disparities in personal capital between Asian/Pacific Islander women and White women. Findings suggest that the risks associated with low socioeconomic status, single motherhood, and low acculturation, rather than race or ethnicity, contribute to low personal capital for many pregnant women. As personal capital during pregnancy may influence subsequent maternal and child health outcomes, the development of interventions should consider addressing sociodemographic and acculturation factors in order to reduce racial and ethnic disparities in personal capital and ultimately in poor maternal and child health outcomes.