Purpose: The psychometric profiles of the widely used International Physical Activity Questionnaire-Short Form (IPAQ-SF) in Chinese youth have not been reported. The purpose of this study was to examine the validity and reliability of the IPAQ-SF using a sample of Chinese youth. Method: One thousand and twenty-one youth (M[subscript age] = 14.26 ± 1.63 years, 52.8% boys) from 11 cities in China wore accelerometers for 7 consecutive days and completed the IPAQ-SF on the 8th day to recall their physical activity (PA) during accelerometer-wearing days. A subsample of 92 youth (M[subscript age] = 15.90 ± 1.35 years, 46.7% boys) completed the IPAQ-SF again a week later to recall their PA during accelerometer-wearing days. Differences in PA estimated by the IPAQ-SF and accelerometer were examined by paired-sample "t" test. Spearman correlation coefficients were used to examine the correlation between the IPAQ-SF and accelerometer. Test-retest reliability of the IPAQ-SF was determined by the intraclass correlation coefficient (ICC). Results: Compared with accelerometer, the IPAQ-SF overestimated sedentary time, moderate PA (MPA), vigorous PA (VPA), and moderate-to-vigorous PA (MVPA). Correlations between PA (total PA, MPA, VPA, and MVPA) and sedentary time measured by 2 instruments ranged from "none" to "low" (? = 0.08-0.31). Test-retest ICC of the IPAQ-SF ranged from "moderate" to "high" (ICC = 0.43-0.83), except for sitting in boys (ICC = 0.06), sitting for the whole sample (ICC = 0.32), and VPA in girls (ICC = 0.35). Conclusion: The IPAQ-SF was not a valid instrument for measuring PA and sedentary behavior in Chinese youth.