Objectives: Identifying adolescents who are at increased risk for a particularly difficult pregnancy and adjustment into parenthood is important, as the physical and psychological development of their infants rest in the well-being of these new mothers. This study aims to examine the effects of prenatal stress and parenting stress and the association with: (1) adolescent maternal adjustment; and (2) postpartum emotional distress. Methods: In a prospective longitudinal cohort study, 154 pregnant adolescents (age 14–19) from 10 public clinics were interviewed four times from the third trimester of pregnancy to 16 months postpartum. Planned comparisons of four stress groups were used to compare mean scores for measures of feelings about motherhood, infant care, parenting competency, and emotional distress. Results: Adolescent mothers who experienced high prenatal stress and high parenting stress had lower maternal adjustment (i.e., fewer positive feelings about motherhood, less infant care, and low parenting competency) and high postpartum emotional distress. Even when compared to adolescent mothers who experienced prenatal or parenting stress only, these adolescents were still at a greater disadvantage. Conclusions: Results suggest that adolescents who experience high stress during and after pregnancy are at increased risk for difficult maternal adjustment and high postpartum emotional distress. Findings support the need for health services targeting this subgroup of adolescent mothers, including both prenatal and parenting support. Early intervention to increase maternal adjustment and decrease emotional distress should remain a priority in facilitating the most optimal maternal and child health outcomes.