Introduction: In studies directed to children and adolescents, the sedentary behavior has been usually represented by exposure to screen, which comprise the total or separate measured time exposed to television, videogame, tablets, mobile devices, and computer. Objective: To analyze the prevalence and factors associated with screen time in children and adolescents. Methods: A cross-sectional school-based study was carried out with 1,471 students from Elementary School, aged between 7 to 18 years (51.3% male), enrolled at public schools (55.6%) in Porto Velho, Rondônia (RO) state, Brazil. Excess screen time was defined as watching television, using the computer, and playing video games for more than two hours per day. Poisson regression was used to obtain crude and adjusted prevalence ratios and their respective 95% CI. Results: Overall prevalence of screen time exposure over two hours per day was 65.9%. After adjustments, risk of screen time exposure was higher in males, PR = 1.51 (95% CI: 1.08 - 1.92), under or equal to 14 years old, PR = 1.69 (95% CI: 1.48 - 1.92), in the 5th grade, PR = 1.41 (95% CI: 1.02 - 1.89), in the 6th grade, PR = 1.44 (95% CI: 1.06 - 1.97) and in the 7th grade, PR = 1.52 (95% CI: 1.09 - 2.13), attending two weekly PE classes or fewer, PR = 1.25 (95% CI: 1.07 - 1.53) ), consuming more than 3 daily meals, PR = 2.69 (95% CI: 2.14 - 3.37) and overweight, PR = 1.51 (95% CI: 1.13 - 2.03). Conclusion: The findings showed that the exposure equal to or more than two hours of daily screen time was high. The students more exposed to this outcome had the next characteristics: male sex, age less than or equal to 14 years, from the fifth, sixth, and seventh grade of elementary education, practice physical education classes less than or equal to two hours per week, consume more than three meals daily and have excess body fat (G%).