Early life stress, daily life experiences, and the stress responsive hypothalamic-pituitary-adrenal (HPA) axis have each been examined as predictors of the development of psychopathology. Rarely have researchers attempted to understand the covariation or interaction among these stress domains using a longitudinal design in the prediction of symptoms of internalizing psychopathology, particularly during childhood. This study examined early family stress, daily interpersonal stress, indicators of diurnal cortisol, and internalizing symptoms in a racially/ethnically and socioeconomically diverse sample of twins (N = 970 children; Mage at outcome = 9.73; 52% female; 23.7% Hispanic/Latino, 58.8% White; 30% below middle class; Lemery-Chalfant et al., 2019). An additive model of stress, a stress mediation model, and a stress sensitization framework model each delineated potential pathways linking stress and internalizing symptoms. Supporting additive pathways, multilevel models showed that all 3 stress indicators uniquely predicted internalizing symptoms. There was a significant indirect path from early family stress to 9 year internalizing symptoms through interpersonal stress, supporting stress mediation. Family stress moderated the association between interpersonal stress and internalizing symptoms, though not in the direction that would support stress sensitization. Child stress, including daily interpersonal stress and HPA axis activity, and internalizing symptoms are prevalent and family stress is a significant precursor to child internalizing symptoms across child development. (PsycInfo Database Record (c) 2022 APA, all rights reserved).