Objective: Greater blood pressure reactivity to psychological stress has been associated with higher risk of developing hypertension. We hypothesised that low stress resilience based on psychological assessment early in life is associated with hypertension in adulthood. Methods National cohort study of 1 547 182 military conscripts in Sweden during 1969-1997 (97-98% of all 18-year-old males) without prior history of hypertension, who underwent standardised psychological assessment by trained psychologists for stress resilience (1-9 scale), and were followed up for hypertension identified from outpatient and inpatient diagnoses during 1969-2012 (maximum age 62). Results 93 028 men were diagnosed with hypertension in 39.4 million person-years of follow-up. Adjusting for body mass index (BMI), family history and socioeconomic factors, low stress resilience at age 18 was associated with increased risk of hypertension in adulthood (lowest vs highest quintile: HR 1.43; 95% CI 1.40 to 1.46; p<0.001; incidence rates, 278.7 vs 180.0 per 100 000 person-years), including a strong linear trend across the full range of stress resilience (ptrend<0.0001). We also found a positive additive interaction between stress resilience and BMI (p<0.001), indicating that low stress resilience accounted for more hypertension cases among those with high BMI. Men with a combination of low stress resilience and high BMI had a more than threefold risk of hypertension. Conclusions These findings suggest that low stress resilience may contribute to etiological pathways for hypertension and accounts for more cases among those with high BMI. If confirmed, this knowledge may help inform better preventive interventions by addressing psychosocial risk factors and stress management across the lifespan.