The Family Stress Model (FSM) is an influential family process model that posits that socioeconomic disadvantage impacts child outcomes via its effects on parents. Existing evaluations of the FSM are constrained by limited measures of socioeconomic disadvantage, cross-sectional research designs, and reliance on non-population-based samples. The current study tested the FSM in a subsample of the Fragile Families and Child Wellbeing Study (N = 2,918), a large population-based study of children followed from birth through age 9. We employed a longitudinal framework and used measures of socioeconomic disadvantage beyond economic resources. Although the hypothesized FSM pathways were identified in the longitudinal model (e.g., economic pressure at age 1 was associated with maternal distress at age 3, maternal distress at age 3 was associated with parenting behaviors at age 5), the effects of socioeconomic disadvantage at childbirth on youth socioemotional outcomes at age 9 did not operate through all of the hypothesized mediators. In longitudinal change models that accounted for the stability in constructs, multiple indicators of socioeconomic disadvantage at childbirth were indirectly associated with youth externalizing behaviors at age 9 via either economic pressure at age 1 or changes in maternal warmth from ages 3 to 5. Greater economic pressure at age 1, increases in maternal distress from ages 1 to 3, and decreases/increases in maternal warmth/harshness from ages 3 to 5 were also directly associated with increases in externalizing behaviors from ages 5 to 9. Results provide partial support for the FSM across the first decade of life.