Objective Transient tachypnea of the newborn (TTN), a common neonatal respiratory morbidity, is associated with failure of adequate clearance of fetal lung fluid. Glucocorticoids have an important role in lung maturity and the mechanisms of lung fluid clearance. The aim of this study is to assess the association between umbilical cord cortisol levels and transient TTN in late preterm and term neonates delivered by elective cesarean section (CS). Study Design A case-control study of 37 newborns diagnosed with TTN (cases) was compared with 40 healthy newborns (controls). All infants were delivered by elective CS without labor. Umbilical cord cortisol levels were measured using enzyme-linked immunosorbent assay. Results Mean cord cortisol levels were significantly lower in cases than controls (131.36 vs. 233.32 nmol/L, p = 0.0001; odds ratio [OR] = 3.7; 95% confidence interval [CI]: 1.40–9.53), respectively. Cord serum cortisol correlated inversely with the duration of tachypnea and the respiratory rate (r =  − 0.678 and −0.535, respectively). Conclusion Umbilical cord cortisol levels are significantly lower in newborns with transient TTN, and lower cortisol levels are associated with an increased respiratory rate and longer duration of admission. Antenatal glucocorticoids can be recommended for late preterm delivered by CS. Key Points