Although quitting smoking lowers the risk of developing chronic conditions, it usually leads to weight gain. Literature on the association between weight gain after quitting smoking and the future development of hypertension is scarce. Among 234 596 individuals who visited our health center, 856 who had quit smoking for whom data were available at least 6 years after smoking cessation were included. We evaluated changes in blood pressure and antihypertensive drug prescription rate at 1 and 6 years after smoking cessation. We also compared weight and blood pressure between the smoking cessation and continued smoking groups after 6 years. Multiple regression analyses were performed to identify predictors of changes in systolic and diastolic blood pressures using covariates affecting blood pressure. Since a median weight gain of 1.8 kg was observed at 1 year after smoking cessation, we divided the participants into high and low-weight gain groups. No significant intergroup difference in the antihypertensive drug prescription rate was observed after 6 years. The high weight gain group showed significant increases in systolic and diastolic blood pressures after 6 years. Multiple regression analyses revealed that systolic blood pressure was affected by age and high weight gain, while diastolic blood pressure was affected by high weight gain. Our findings suggest that weight gain following smoking cessation leads to blood pressure elevation: the smoking cessation group gained more weight and had higher blood pressure than the continued smoking group. Therefore, weight loss guidance may be useful for individuals who want to quit smoking. Participants in the high weight gain group showed significant increases in systolic and diastolic blood pressures at 6 years after smoking cessation that were significantly different from those observed in participants in the low weight gain group and the continued smoking group.