High blood pressure early in life is associated with cardiovascular disease morbidity and mortality in adulthood. The objective was to identify sex-specific trajectories of SBP and DBP from early adolescence to early adulthood and to assess the impact of modifiable factors on the trajectories, including BMI, smoking, alcohol use, physical activity, and screen-time. Data were drawn from four waves of a prospective investigation of 1294 youth aged 12-13 years at inception and followed until age 24 years. Group-based trajectory models were used to identify trajectories and assess the impact of modifiable factors in 403 men and 432 women. Three SBP trajectories were identified in men [corresponding to low (43.2%), medium (45.2%), and high SBP (11.7%)] and women [corresponding to low (48.1%), medium (44.7%), and high SBP (7.2%)]. Similar results were observed for DBP in both sexes. BMI and smoking were associated with higher SBP and DBP values in most trajectory groups, whereas screen-time in both sexes and physical activity in women were associated with high SBP trajectories only. There is heterogeneity in the sex-specific natural course of SBP and DBP in youth and in the magnitude of the effect of modifiable factors on SBP and DBP across trajectories. Distinguishing trajectories allows identification of subgroups at risk of hypertension and cardiovascular disease later in life and in addition can inform the design of targeted interventions to attenuate high SBP and DBP trajectories over time and maintain normal trajectories.