Effective and sustained blood pressure (BP) control in hypertensive patients with moderate-to-severe obesity is often difficult to achieve. We evaluated clinic, 24h, day-time and night-time systolic/diastolic BP levels and control in a large cohort of adult outpatients with different classes of obesity. A single center, prospective, cohort study was conducted at Hypertension Unit, Division of Cardiology, Sant'Andrea Hospital, Rome Italy. All BP measurements were performed and BP thresholds were set according to guidelines. Study population was stratified according to BMI. We included 4,766 individuals (women 48.6%, age 60.3 ± 11.6 years, clinic BP 143.8 ± 18.2/90.9 ± 12.3 mmHg, 24h BP 130.2 ± 13.3/79.1 ± 9.5 mmHg), among whom 36.0% had normal weight, 43.5% were overweight, 15.7% had class I, and 4.8% class II/III obesity. Obese outpatients had higher prevalence of risk factors, and were treated more frequently and with more antihypertensive drugs than those with normal body weight. Obese outpatients showed higher systolic BP levels at all BP measurements, mostly 24h and night-time periods, than those observed in normal weight outpatients. BMI resulted significantly related with clinic (r = 0.053; P < 0.001), 24h (r = 0.098; P < 0.001) and night-time systolic BP (r = 0.126; P < 0.001), and left ventricular mass indexed by height^2.7 (r = 0.311; P < 0.001). BMI was also negatively and independently associated with predefined BP goals at all types of BP measurements. Obesity was associated with higher systolic BP levels during the entire 24h period and increased left ventricular mass. These effects were independently observed, even after correction for major cardiovascular risk factors and comorbidities, as well as the number and type of antihypertensive drug classes.