To assess the association between age of juice introduction and child anthropometry after the American Academy of Pediatrics changed their guidelines in 2017 to recommend delaying juice introduction until at least 12months of age (previously 6months), citing concerns of weight gain. Upstate KIDS is a prospective birth cohort with follow-up through 9years of age. Juice introduction was assessed on parental questionnaires at 4-18months and categorized as <6, 6-<12, and ≥12months. Child height and weight were recorded at 2-3 and 7-9years of age. Weight-, height-, and body mass index (BMI)-for-age and sex z scores were calculated using the Centers for Disease Control and Prevention reference. Overweight/obese and obese status were categorized as BMI-for-age z score ≥85th and ≥95th percentiles. Controlling for sociodemographic characteristics and parental BMI, we assessed the associations of age of juice introduction with child anthropometry. Prevalence of childhood obesity was 16.4% at 2-3 (n=1713) and 22.8% at 7-9years of age (n=1283). Juice introduction at <6 vs≥12months was associated with higher weight-for-age z score at 2-3years of age (mean difference=0.21; 95% CI 0.04-0.37). At 7-9years of age, juice introduction at <6 vs≥12months was related to higher BMI-for-age (0.38; 0.12-0.64) and weight-for-age z scores (0.27; 0.06-0.49). Risk of developing overweight/obesity and obesity was 1.54 (0.99-2.38) and 2.17 (1.11-4.23) times higher among children with juice introduced at <6months. No associations were found with juice introduced at 6-<12 vs≥12months. Risk of developing overweight/obesity or obesity is higher among children introduced to juice before 6months of age compared with ≥12months.