Background: According to the current physical activity (PA) recommendations, children should accumulate 60 minutes of moderate to vigorous PA (MVPA) throughout the day, 30 minutes of MVPA during the school hours, and 50% of the recess time in MVPA. Our aim was to examine the temporal trends of accelerometer-based PA during the previously mentioned day segments and the proportion of children who met the PA recommendations. Methods: This was a cross-sectional study with 2 independent samples: 499 fourth graders (49.2% females) in 2011–2012 and 364 fourth graders (46.9% females) in 2017–2018. Hip-worn accelerometers were used to assess PA. Results: A decline in light PA, moderate PA, vigorous PA, MVPA, and total PA during whole day, and in the rate of compliance with daily MVPA recommendations in males (P < .01) was observed from 2011–2012 to 2017–2018. Females decreased their daily light PA and moderate PA (P < .05). A decline in all PA variables during school hours in both sexes (P < .05) and in the rate of compliance with the 30 minutes of MVPA recommended during school hours in males (P < .001) were observed. There were no differences in PA during recesses. Conclusions: Interventions are needed to attenuate the temporal decrease in PA levels in children.