Sedentary behavior is a recognized risk factor for chronic diseases, including obesity, type 2 diabetes, and cardiovascular disorders, and is considered the fourth leading cause of death worldwide. In Algeria, despite a growing prevalence of sedentary lifestyles, few studies have focused on urban populations, such as Constantine, to explore the links between sedentary behavior, physical activity, and health indicators. This cross-sectional study, conducted in 2019, investigates these relationships among 437 participants aged 18–75 years, using the International Physical Activity Questionnaire (IPAQ). Results reveal that 37.8% of participants were sedentary and 62.2% active. Sedentary individuals were older (46.23 ± 16.51 vs. 42.79 ± 15.00 years, p = 0.02), had higher BMI (26.28 ± 4.42 vs. 25.40 ± 3.78 kg/m², p = 0.024), and larger waist circumference (91.99 ± 15.10 vs. 88.49 ± 13.32 cm, p = 0.005). Smoking was more prevalent in sedentary participants (62.19% vs. 37.80%, p = 0.01), while hypertension was more common in active individuals (68.18% vs. 31.81%, p = 0.05). Education strongly correlated with activity level (p < 0.0001) . These findings highlight the urgent need for public health strategies aimed at reducing sedentary behavior and promoting physical activity, tailored to the socio-economic and demographic context of Constantine.