<p><strong>OBJECTIVES: </strong>The validity of the Global Physical Activity Questionnaire has not been thoroughly evaluated among Hispanics/Latinos. In this cross-sectional study, we assessed the concurrent validity and correlates of discordance of the Global Physical Activity Questionnaire by comparing it to accelerometry in estimating sedentary behavior, moderate-to-vigorous physical activity, and meeting United States physical activity guidelines by sociodemographic, behavioral, and health characteristics.</p><p><strong>DESIGN: </strong>The Hispanic Community Health Study/Study of Latinos is a 4-site cohort study of United States adults aged 18-74 years enrolled from 2008 to 2011.</p><p><strong>METHODS: </strong>Participants (n = 11,873) completed the Global Physical Activity Questionnaire and wore an accelerometer for 1 week. Lin's concordance and Pearson correlations assessed concurrent validity between self-reported and accelerometry-assessed measures of sedentary behavior and moderate-to-vigorous physical activity. Kappa coefficients assessed agreement of meeting physical activity guidelines. Linear and logistic regression models identified correlates of discordance.</p><p><strong>RESULTS: </strong>The overall Lin's concordance and Pearson correlations between the Global Physical Activity Questionnaire and accelerometry estimates were 0.10 (95 % confidence interval 0.09, 0.12) and 0.24 (0.21, 0.27) for sedentary behavior, and 0.04 (0.03, 0.05) and 0.18 (0.15, 0.22) for moderate-to-vigorous physical activity, respectively. Agreement was poor for meeting the physical activity guideline classifications (Kappa coefficients: 0.12 to 0.26). Over a 16-hour day, sedentary behavior was under-reported by 3.8 h and moderate-to-vigorous physical activity was over-reported by 1.9 h.</p><p><strong>CONCLUSIONS: </strong>The concurrent validity of the Global Physical Activity Questionnaire in measuring moderate-to-vigorous physical activity and sedentary behavior when compared to accelerometry was poor among Hispanic/Latino adults.</p>