Background: Synthetic glucocorticoid exposure in late pregnancy may be associated with higher blood pressure in offspring. We hypothesized that endogenous cortisol in pregnancy relates to offspring blood pressure (OBP). Objective: To investigate associations between maternal cortisol status in third trimester pregnancy and OBP. Methods: We included 1317 mother-child pairs from Odense Child Cohort, an observational prospective cohort. Serum (s-) cortisol and 24-hour urine (u-) cortisol and cortisone were assessed in gestational week 28. Offspring systolic blood pressure and diastolic blood pressure were measured at age 3, 18 months, and 3 and 5 years. Associations between maternal cortisol and OBP were examined by mixed effects linear models. Results: All significant associations between maternal cortisol and OBP were negative. In boys in pooled analyses, 1 nmol/L increase in maternal s-cortisol was associated with average decrease in systolic blood pressure (β=−0.003 mmHg [95% CI, −0.005 to −0.0003]) and diastolic blood pressure (β=−0.002 mmHg [95% CI, −0.004 to −0.0004]) after adjusting for confounders. At 3 months of age, higher maternal s-cortisol was significantly associated with lower systolic blood pressure (β=−0.01 mmHg [95% CI, −0.01 to −0.004]) and diastolic blood pressure (β=−0.010 mmHg [95% CI, −0.012 to −0.011]) in boys after adjusting for confounders, which remained significant after adjusting for potential intermediate factors. Conclusions: We found temporal sex dimorphic negative associations between maternal s-cortisol levels and OBP, with significant findings in boys. We conclude that physiological maternal cortisol is not a risk factor for higher blood pressure in offspring up to 5 years of age.