The nationally representative Early Childhood Longitudinal Study-Birth cohort data set was used to compare parenting behaviors of adolescent mothers (less than 19 years old), emerging adult mothers (19-25 years old), and adult mothers (greater than 25 years old) when their children were 2 years old. Regression models controlling for socioeconomic differences indicate that adolescent mothers exhibited less supportiveness, sensitivity, and positive regard than emerging adult mothers, who exhibited less than adults. Adolescent and emerging adult mothers reported comparable frequencies of spanking and use of time out but significantly more than adults. Age differences in coparenting were largely accounted for by different rates of father coresidence. These finding suggest that age differences in parenting behaviors are not solely explained by sociodemographic factors, and that mothers who gave birth during the emerging adult period are a developmentally distinct group; overall, they are not as prepared for optimal parenting as older mothers but are better equipped than adolescent mothers. (Contains 4 tables.)