The authors analyzed time trends and sociodemographic inequalities in different physical activity and sedentary behavior domains between 2003 and 2019. A secondary analysis of data from 5 cross-sectional Brazilian epidemiological surveys (World Health Survey—2003, National Household Sample Survey—2008/2015, and Brazilian Health Survey—2013/2019) conducted among a nationally representative sample of Brazilian adults. The authors used data on different domains of physical activity (leisure, commute, total transport, and total physical activity) and sedentary behavior (TV viewing and other types of screens) that were available in the different surveys. Gender, age group, country region, ethnicity, type of area and city, and quintiles of income and educational achievement were used as sociodemographic correlates. The prevalence of leisure-time physical activity increased over time (2008: 7.0% vs 2019: 26.5%). There was also an increased trend of social inequality in leisure-time physical activity. A trend of reduction was observed for active commuting (2008: 35.0% vs 2019: 21.8%), while total transport physical activity was stable (2013: 49.5% vs 2019: 49.6%). Directions of findings were opposite for sedentary behavior, with reduced trend for >3 hours per day of TV viewing (2008: 34.8% vs 2019: 21.8%) and increased trend for >3 hours per day of other types of screen time (2008: 6.4% vs 2019: 22.2%). A positive trend exists in leisure-time physical activity, but there was also an increase in social inequalities for physical activity in Brazil.