OBJECTIVE: To examine the association between breakfast consumption and physical activity in a well-characterised sample of English children. DESIGN: Cross-sectional study using food diaries to record breakfast consumption and accelerometry to assess physical activity. SETTING: Norfolk county, England. SUBJECTS: Children (n 1697) aged 9-10 years from the SPEEDY (Sport, Physical Activity and Eating behaviour: Environmental Determinants in Young people) study. RESULTS: Boys who consumed a poor-quality breakfast based on dairy product, cereal and fruit intakes spent approximately 7 min more time in moderate-to-vigorous physical activity (MVPA) during weekday afternoons and evenings compared with those who did not consume breakfast (P < 0·05). On weekend days, boys who consumed a poor- or good-quality breakfast spent approximately 6 and 5 min less time respectively being sedentary during the mornings compared with breakfast non-consumers (P < 0·05). Boys who consumed a good-quality breakfast spent almost 3 min more in MVPA during the morning on weekend days compared with non-consumers, and boys who consumed a poor- or good-quality breakfast were 22 % and 16 % more active overall respectively than breakfast non-consumers (P < 0·05). During the rest of the day, boys who consumed a good-quality breakfast spent about 11 min less time being sedentary (P < 0·05) and 7 min more time in MVPA (P < 0·01). CONCLUSIONS: Although some associations between breakfast consumption and physical activity were detected for boys, the present study does not provide strong evidence that failing to consume breakfast, or having a low energy intake at breakfast time, is detrimental to children's physical activity levels.