BackgroundData on the impact of age at onset of overweight/obesity on the risk of hypertension are limited. We aimed to investigate the above-mentioned association in Chinese population.Methods6700 adults who participated in at least three survey waves and were free of overweight/obesity and hypertension on first survey were included using China Health and Nutrition Survey. The age of participants at the onset of overweight/obesity (body mass index ≥ 24 kg/m2) and subsequent hypertension occurrence (blood pressure ≥ 140/90 mmHg or use of antihypertensive medication) were identified. We used the covariate-adjusted Poisson model with robust standard error to calculate the relative risk (RR) and 95% confidence interval (95%CI) to examine the relationship between the age at onset of overweight/obesity and hypertension.ResultsThere were 2,284 new-onset overweight/obesity cases and 2,268 incident cases of hypertension during an average 13.8-year follow-up period. Compared with the population without overweight/obesity, the RR (95% CI) of hypertension was 1.45 (1.28–1.65), 1.35 (1.21–1.52) and 1.16 (1.06–1.28) for overweight/obesity onset in participants aged < 38 years, 38–47 years, and ≥ 47 years, respectively. The risk of hypertension increased linearly with a decrease in age at onset of overweight/obesity (P< 0.001 for trend). The sensitivity analyses results were similar after excluding the participants taking antihypertensive medications or those with new-onset obesity or using waist circumference to define overweight/obesity.ConclusionsOur results emphasize the importance of assessing age at onset of overweight/obesity to prevent hypertension.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12872-023-03347-z.