Abstract This study analyzed the validity and reliability of an instrument with scales measuring factors associated with screen time in adolescents. Two cross-sectional studies included students for analyses of validity and internal consistency (n=1138, 51.5% boys) and test-retest reproducibility (n=194, 56.2% boys). Individual (attitude, self-efficacy and expectations), social (behaviors, rules, beliefs and family support and support of school members) and physical environmental (home and bedroom equipment) factors of screen time were evaluated. All the scales of the instrument met the statistical criteria of the validity of the exploratory factorial analysis (p<0.001). The exploratory factorial analysis indicated five one-dimensional and three two-factor scales (self-efficacy, expectations and familiar behavior), with factorial loads of 0.56 to 0.88. There were significant correlations between the scores of almost all the scales and the reported screen time (p<0.05). Eight of nine scales/subscales showed Cronbach’s α value being higher than 0.70, and ICC ranged from 0.63 to 0.83. In conclusion, the instrument presented scales with acceptable validity and reliability and can be used to measure factors associated with screen time in Brazilian students.