Poverty and single parent status, which often co-occur, have been shown to relate to lower effortful control, and this may be in part due to disruptions in hypothalamic– pituitary– adrenal (HPA) axis activity. Both poverty and single parent status may compromise parenting, which in turn may disrupt HPA axis activity and the development of effortful control. We examined whether parenting and HPA axis activity accounted for the effects of poverty and single parent status on the development of effortful control in preschool children (N = 78). Effortful control was measured at two time points, 6months apart. Individually, poverty and single parent status were related to blunted HPA axis activity, characterized by low AM and PM cortisol. However, when examined together, the effects were present only for preschoolers whose parents were in poverty. Parental warmth and negativity accounted for the relations between poverty and blunted cortisol. Blunted cortisol was related to lower effortful control at Time 2. These results suggest a pathway through which poverty may impact children’ s developing effortful control through parenting, which in turn may shape HPA axis activity.