This study examined seasonal differences in children's segmented-day physical activity (PA) and time engaged in sedentary activities. Seventy-three children wore a pedometer during winter and spring and completed a diary relating to their after-school sedentary activities and time playing outside. Children recorded higher steps in spring compared to winter (p < 0.05). Boys recorded higher steps in winter during the before-school period and break time, but girls recorded higher steps in spring during these periods (p < 0.05). Children reported more minutes per day playing outside (p < 0.05), and less time studying (p < 0.001) and attending private lessons (p < 0.05) in spring compared to winter. No seasonal differences were recorded in screen-related sedentary behaviours. Children's PA levels should be especially targeted during the winter months. In Cyprus, schools may consider giving priority to girls to use indoor/covered facilities in winter and to boys in spring. Interventions to reduce screen-related sedentary behaviours should be applied throughout the year.