Background: Nighttime blood pressure (BP) was reported to have a stronger association with cardiovascular outcome and hypertensive organ damage than clinic BP, 24-hour BP, and daytime BP in hypertensives. However, the significance of nighttime BP was not established in stage B heart failure (HF) patients. We hypothesized that nighttime BP measured by home BP monitoring device was associated with cardiovascular outcome in stage B HF patients. Method: We used the dataset of Japan Morning Surge-Home Blood Pressure study (J-HOP study), and selected 417 of stage B HF patients. The definition of stage B HF was based on Universal definition of HF. The patients with history of HF hospitalization were excluded. BP was measured on waking, before bedtime and during the night. The cardiovascular event was followed. Result: Mean follow-up period was 6.6±3.8 years, and 59 cardiovascular events were occurred. When nighttime hypertension was defined as nighttime BP >120mmHg, nighttime HT group showed higher BMI, serum creatinine, HbA1c, and higher prevalence of diabetes, atrial fibrillation, and chronic kidney disease, and lower HDL-cholesterol than nighttime normotension (NT) group. With regard to BP, nighttime HT group, clinic BP, home morning BP, home evening BP, and home nighttime BP were higher in nighttime HT group than in nighttime NT group. In Kaplan-Meier analysis, nighttime HT group had a higher incident of cardiovascular event than nighttime NT group (P<0.01). In Cox multivariate analysis, nighttime HT was significant predictor for cardiovascular event adjusting by significant variables (Hazard ratio 1.84, 95% Confidence interval: 1.01-3.36, P=0.046). Conclusions: Nighttime HT was a prognostic factor in stage B HT patients. Nighttime BP was a therapeutic target to improve the outcome in stage B HT patients.