AIM: Accumulating evidence reveals that sedentary behavior is associated with mortality and cardiometabolic disease; however, there are potential age and sex differences in sedentary behavior and health outcomes that have not been adequately addressed. This study aimed to determine the association of sedentary behavior with cardiometabolic diseases such as hypertension, dyslipidemia, diabetes mellitus, and its risk factors in a large Japanese population according to age and sex. METHODS: Using data from the Japan Multi-Institutional Collaborative Cohort Study obtained from baseline surveys, data of 62,754 participants (27,930 males, 34,824 females) were analyzed. This study uses a cross-sectional design and self-administered questionnaires to evaluate sedentary time and anamnesis. For the logistic regression analysis, sedentary time ＜5 h/day was used as the reference and then adjusted for age, research areas, leisure-time metabolic equivalents, and alcohol and smoking status. From the analysis of anthropometric and blood examinations, 35,973 participants (17,109 males, 18,864 females) were analyzed. RESULTS: For hypertension and diabetes, sedentary time was associated with a significantly higher proportion of male participants. Both sexes were associated with a significantly higher proportion of participants with dyslipidemia. Participants who had longer sedentary time tended to have increased levels of blood pressure, triglycerides, and non-high-density lipoprotein cholesterol (HDL-C), and decreased levels of HDL-C, especially in the 60-69 years group. CONCLUSIONS: Independent of leisure-time physical activity, sedentary time was associated with cardiometabolic diseases in a large Japanese population classified by age and sex. Our findings indicate that regularly interrupting and replacing sedentary time may contribute to better physical health-related quality of life.