To compare pre- and post-stress salivary cortisol levels in adolescents born preterm to those born term and to assess the influence of race and sex on this relationship.We measured salivary cortisol before and 20 min after a maximal-exercise stress test and calculated the cortisol stress response. We used linear regression to compare cortisol stress responses between preterm and term groups, adjusting for birth weight z-score and maternal hypertension, and examined effect modification by race and sex.We evaluated 171 adolescents born preterm with very low birth weight and 50 born term. Adolescents born preterm had reduced cortisol stress response compared to term (0.03 vs. 0.08 μg/dL, p = 0.04). This difference was race dependent: non-Black adolescents born preterm had significantly reduced cortisol stress response compared to those born at term (adjusted β: -0.74; 95% CI -1.34, -0.15), while there was no difference in Black adolescents (0.53; -0.16, 1.22). Sex did not modify the relationship.Adolescents born preterm exhibit a reduced salivary cortisol response to exercise stress, suggesting long-term alterations in the hypothalamic-pituitary-adrenal axis. This relationship was evident in non-Black but not in Black adolescents, suggesting that race may modify the influence of preterm birth on stress alterations of the hypothalamic-pituitary-adrenal axis.