Physical activity (PA) has rarely been quantified in adolescent populations undergoing economic transition; therefore relationships with disease still remain uncertain. This study assessed whether absolute PA energy expenditure (PAEE), PAEE/kg, and PAEE/kg(FFM) could be accurately estimated using accelerometry and a questionnaire in Indian adolescents and how these values compared to those of other populations. PAEE was assessed using doubly labeled water (DLW) in 30 adolescents from Chennai, India, over seven consecutive days, simultaneous with the measurement of PA using accelerometry and a previous-week recall questionnaire. Accelerometry counts (regression analysis) and questionnaire data were used to estimate PAEE; estimates were cross-validated using the Bland-Altman method. Accelerometry data and DLW-derived PAEE were visually compared to values from four North American and European populations. For boys, 49% of the variance in DLW-derived PAEE was explained with an equation including accelerometry counts and fat-free mass (FFM). Questionnaire-derived estimates did not contribute to the explained variance in DLW derived PAEE. The group-level PA of these Indian adolescents was successfully assessed using accelerometry, but not questionnaire. DLW-derived PAEE/kg(FFM) (mean (s.d.): 53.0 (27.5) kJ/kg(FFM)/day) was lower in this group than other adolescent populations in Europe and similar to those in North America. Additionally, four boys and none of the girls accumulated ≥60 min/day of accelerometry-derived moderate intensity activity, indicating low levels of PAEE and PA in these adolescents. Further research is necessary to investigate the association between PA and health outcomes in Indian adolescents.