Hypertension is common in adults and often undiagnosed, and the prevalence of pre- and undiagnosed-hypertension remains unclear. We aimed to investigate the prevalence of pre- and undiagnosed-hypertension and their correlates among urban Chinese adults. A total of 7435 participants aged 20-79 were included in this study. Data on demographics, lifestyle and medical history were collected through a structured interview. Pre- and undiagnosed-hypertension was defined as systolic blood pressure/diastolic blood pressure (SBP/DBP) of 120-139/80-89 mm Hg and SBP >= 140 mm Hg and/or DBP >= 90 mm Hg, respectively, in participants without a history of hypertension and use of antihypertensive medication. Prevalence rates were calculated and standardized using local age- and gender-specific census data. Data were analysed using multinomial logistic regression with adjustment for potential confounders. Of all the participants, 2726 (36.7%) were diagnosed with pre-hypertension and 919 (12.3%) with undiagnosed hypertension. Undiagnosed-hypertension accounted for 37.3% of all participants with hypertension. The prevalence of prehypertension gradually decreased with age, while undiagnosed-hypertension increased, although presenting different changing patterns among men and women. In a fully adjusted multinomial logistic regression, age, male sex, low socio-economic status (SES), abdominal obesity, alcohol drinking, physical inactivity and type 2 diabetes mellitus (T2DM) were significantly associated with increased odds of pre- and undiagnosed-hypertension. In conclusions, the prevalence of pre- and undiagnosed-hypertension was -50% among urban Chinese adults. Abdominal obesity, low SES, alcohol drinking, physical inactivity and T2DM may be indicators for pre- and undiagnosed-hypertension.