Objective To know how confinement affects children’s routines, more specifically their physical activity (PA) and sedentary time.MethodsAn online survey was launched to assess how Portuguese children under 13 years of age are adjusting their daily routines to confinement. Parents reported the daily time each child was engaged in different activities, which were used to calculate overall sedentary time and overall physical activity time.Results: Data from 2159 children, indicated that during confinement: i) there was a decrease in children’s physical activity time (72.3%); and an increase in screen time (71.3%) and family activities (83.9%); ii) the only sex differences were found on Playful Screen Time (boys > girls) and in Play without PA (girls > boys); iii) along age groups, there was a trend for the increase of the overall sedentary time and a complementary decrease of overall physical activity time (both F(3,2097) =97.951, p < .001).Conclusion: Overall, PA of confined children showed low levels and a clear decreasing trend along childhood. Conjoint family and societal strategies to target specific age groups should be organized in the future.