ObjectiveTo explore the relationship between changing occupational stress levels, hair cortisol concentration (HCC), and hypertension.MethodsBaseline blood pressure of 2520 workers was measured in 2015. The Occupational Stress Inventory—Revised Edition (OSI-R) was used to assess changes in occupational stress. Occupational stress and blood pressure were followed up annually from January 2016 to December 2017. The final cohort numbered 1784 workers. The mean age of the cohort was 37.77±7.53 years and the percentage male was 46.52%. At baseline, 423 eligible subjects were randomly selected for hair sample collection to determine cortisol levels.ResultsIncreased occupational stress was a risk factor for hypertension [risk ratio (RR) = 4.200, 95% confidence interval (CI): 1.734–10.172]. The HCC of workers with elevated occupational stress was higher than that of workers with constant occupational stress [(ORQ score ≥70: geometric mean±geometric standard deviation = 5.25±3.59 ng/g hair; 60–90: 5.02±4.00; 40–59: 3.45±3.41; <40: 2.73±3.40)x2= 5.261]. High HCC increased the risk of hypertension (RR = 5.270, 95% CI: 2.375–11.692) and high HCC was associated with higher rates of elevated diastolic and systolic blood pressure. The mediating effect of HCC was 0.51[(95% CI: 0.23–0.79, odds ratio(OR) = 1.67] and accounted for 36.83% of the total effect.ConclusionsIncreased occupational stress could lead to an increase in hypertension incidence. High HCC could increase the risk of hypertension. HCC acts as a mediator between occupational stress and hypertension.