Background and AimsPrevious studies have investigated the concordance between objective and subjective measures for assessing physical activity, sedentary behaviour, and sleep duration separately. However, no studies have compared adherence to the 24-hour movement guidelines using both objective and subjective measures in adolescents. The aim of this study was to compare adherence to the 24-hour movement guidelines using both objective and subjective measures MethodsA comprehensive search was conducted in PubMed, Scopus, Web of Science, EMBASE, CINAHL, and SPORTDiscus up to May 2024. A meta-analysis using a random-effects model was conducted, and a p-value of <0.05 was considered statistically significant. ResultsOf the 5,968 studies identified, only 42 met the inclusion criteria, with the included studies reporting a mean age of participants ranging from 11.99 to 17.99 years, comprising a total sample of 856,235 participants. There was no statistically significant difference between objective and self-reported measures of adherence to the 24-hour movement guidelines (p>0.05). When analysing each behaviour separately, there was a statistically significant difference between objective and self-reported measures of physical activity and sleep time (p<0.05). Regarding sedentary behaviour, all studies used subjective measures; therefore, no meta-analysis was performed for screen time as all studies relied on subjective measures. ConclusionBased on these findings, both objective and subjective measures can be used to assess adherence to the 24-hour movement guidelines in adolescents. Thus, researchers and policymakers can choose either objective or subjective methods to assess adherence to the 24-hour movement guidelines, with decisions tailored to the clinical context.