Early and prolonged exposure to poverty disrupts biological processes associated with the body’s stress response system, leading to long-term negative health outcomes, including obesity, autoimmune disorders, and cardiovascular disease. Allostatic load (AL), a composite measure of chronic stress on the body, is a robust predictor of subsequent health outcomes. However, developmental research examining the associations of early poverty exposure with AL in adolescence, as well as the underlying mechanisms of influence is limited. Early poverty exposure also impedes healthy development of child self-regulation, which may increase risk for high AL in adolescence, but this mechanistic pathway has not yet been tested. We used data from the national Study of Early Child Care and Youth Development (SECCYD) to examine the longitudinal associations between prolonged poverty exposure in early childhood (0–3 years) and AL in adolescence (age 15). We also tested the mediating role of child delay of gratification, a behavioral measure of self-regulation (at age 54 months), in the potential association between early poverty exposure and adolescent AL. Accounting for model covariates (i.e., child biological sex and race-ethnicity) and individual differences in child delay of gratification, early and prolonged poverty exposure was significantly associated with higher AL at age 15. The indirect effect through child delay of gratification was not significant, but the individual pathways of the indirect effect were significant, and the overall direct association of early poverty exposure with adolescent AL was significant. Our findings show that prolonged exposure to poverty in early childhood (0–3 years) can have significant negative associations with both child delay of gratification (at 54 months) and AL (at age 15). Given that the detrimental impacts of poverty exposure can be detected at an early age, targeted prevention efforts (e.g., anti-poverty programs such as cash assistance programs) may be able to offset some of the risks of early poverty exposure on self-regulation and AL.