Abstract This study examined concurrent changes in all components of 24-h movement behaviours (24-h MB) (sleep, sedentary behaviour [SB] and physical activity [PA]) and compliance with the Australian 24-Hour Movement Guidelines over the primary to the secondary school transition period. The analytical sample included 83 children (60.2% girls) who provided valid accelerometer-measured 24-h MB data during their final year of primary school (T1) and first year of secondary school (T2). Self-reported participation in domain-specific SB and PA, socio-demographic characteristics and weight status were also assessed. Change in 24-h MB composition from T1 to T2 was analysed using a compositional multivariate linear model for repeated measures. The difference in the proportion of meeting the 24-hour integrated movement guidelines was assessed using a McNemar–Bowker test. An unfavourable change was observed in the 24-h MB composition (p