Introduction: Sedentary behavior is closely related to health problems, especially non-communicable diseases (NCD). However, in Indonesia, the total time spent in sedentary behavior has not been quantitatively measured. This study aims to measure the amount of sleep and sedentary behavior in adolescence objectively. Methods: This study sample consisted of 47 Indonesian high school students aged between 16 and 18 years old, consisting of 24 males and 23 females. Data on sedentary behavior and sleep time were even-day ActivPAL data. The recording was carried out for 24 hours every day. Results: The results showed significant differences in sleep between boys and girls (8.3 + 1.44 vs. 9.3 + 1.41, P <.05). The behavior between female adolescents and males in Indonesia is also significantly different (10.3 + 1.24 vs. 9.3 + 1.37, P <.05). Conclusion: Girls spend an average of more sleep per day than boys, and boys’ sedentary behavior time is higher than girls’. These findings indicate the need for the promotion of appro- priate sedentary behaviours and sleeping time in adolescents.