Hypertension after heart transplantation (HTx) is common. We investigated predictors of and mechanisms for hypertension development during the first year after HTx, with particular attention toward immunosuppressive agents, reinnervation processes, and donor/recipient sex. Heart transplant recipients (HTxRs) were consecutively enrolled 7 to 12 wk after surgery and followed prospectively for 12 mo. Ambulatory blood pressure recordings and autonomic cardiovascular control assessments were performed at baseline and follow-up. Possible predictors of posttransplant hypertension development were investigated in bivariate linear regression analyses followed by multiple regression modeling. A total of 50 HTxRs were included; 47 attended the follow-up appointment at 12 mo. Mean systolic and diastolic blood pressure increased significantly during the observational period (systolic blood pressure from 133 to 139 mm Hg, P  = 0.007; diastolic blood pressure from 81 to 84 mm Hg, P  = 0.005). The blood pressure increment was almost exclusively confined to HTxRs with a female donor heart, doubling the cases of systolic hypertension (from 6 to 13/14; 46% to 93%, P  = 0.031) and diastolic hypertension (from 7 to 14/14; 54% to 100%, P  = 0.031) in this subgroup. Autonomic cardiovascular control assessments suggested tonically constricted resistance and capacitance vessels in recipients with female donor hearts. Immunosuppressive agents and reinnervation markers were not associated with hypertension development. Blood pressures increase during the first year after HTx, with female donor sex as a strong predictor of recipient hypertension development. The underlying mechanism seems to be enhanced peripheral vasoconstriction caused by attenuated cardiovascular homeostasis capabilities. Further studies are needed to confirm the results.