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 _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_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” (ρ = .08–.31). Test–retest ICC of the IPAQ–SF ranged from “moderate” to “high” (ICC = .43–.83), except for sitting in boys (ICC = .06), sitting for the whole sample (ICC = .32), and VPA in girls (ICC = .35). Conclusion: The IPAQ–SF was not a valid instrument for measuring PA and sedentary behavior in Chinese youth.