Objective. To examine characteristics of the infant and mother associated with rapid infant weight gain (RIWG). Methods. Electronic health records (N = 4626) of term infants born were reviewed. Multivariable logistic regression examined the presence of RIWG (vs not) using participant characteristics in the whole sample and in stratified groups. Results. The prevalence of RIWG was 18.7%. Predictors of RIWG were infant male sex, younger infant gestational age, firstborn (vs later born) status, maternal Black or Other (Asian, American Indian, etc), non-Hispanic race/ethnicity (vs White non-Hispanic), Medicaid (vs non-Medicaid insurance), and maternal cigarette smoking status (vs never smoker). The regression model explained between 7.0% and 11.4% of the variance in RIWG. There were few differences in predictors of RIWG in stratified samples. Conclusions. Early childhood obesity intervention efforts may target the modifiable risk factors for RIWG starting prenatally.