Background: Evidence is lacking on the relative contributions of specific lifestyle factors and their overall contribution to prevention of hypertension, in particular early-onset hypertension. Methods: This prospective cohort study included participants of the Nurses’ Health Study (NHS, N=52,780 women, aged 40–67 in 1986), the NHS II (N=83,871 women, aged 27–46 in 1991), and the Health Professionals Follow-up Study (HPFS, N =31,269 men, aged 40–75 in 1986), who were free from hypertension, cardiovascular disease and cancer at baseline. Four modifiable lifestyles were evaluated based on hypertension guidelines: BMI, moderate-to-vigorous physical activity, Dietary Approaches to Stop Hypertension (DASH) score, and alcohol intake. Primary outcome was incident self-reported diagnosis of hypertension with 27-31 years of follow-up. Results: Each lifestyle factor was associated with incident hypertension in dose-dependent manners across the cohorts, with BMI having the strongest associations. On average, adhering to BMI <25 kg/m2 was associated with 20.3 [18.5, 22.0], 25.0 [23.2, 26.8], and 18.6 [16.7, 20.7] months longer periods free from hypertension during 25-year follow-up in each cohort respectively. BMI accounted for approximately 20% of incident hypertension in NHS and HPFS, and 35% of early-onset hypertension (age < 55y). Moderate-to-vigorous physical activity and diet accounted for 10-15% of incident hypertension in women, and the contributions were greater for early-onset hypertension. Conclusion: Healthy weight during adulthood was most substantially associated with incident hypertension among lifestyle factors, but diet, physical activity, and alcohol intake were also related to the risk across all ages, and hypertension-free periods, with stronger associations in early-onset hypertension.