The aim of this study was to verify the relation between body mass index (BMI) and sitting time in a sample of 4,091 Azorean men. BMI was calculated from self-reported weight and height. Total physical activity (PA) time and total sitting time were assessed with the IPAQ (short version). Linear Regression analysis showed that total sitting time (hours/day) was positively associated with BMI (B = 0.078; p < 0.001) after adjustments for age, meal frequency, alcohol and tobacco consumptions, island of residence, education level and total PA time. Although the cross sectional design precludes us from establishing causality, our findings emphasize the importance of reducing sedentary behavior to decrease the risk of obesity.