Parks and park features are important for promoting physical activity and healthy weight, especially for low-income and racial/ethnic minority youth who have disproportionately high obesity rates. This study 1) examined associations between neighborhood park and playground availability and youth obesity, and 2) assessed whether these associations were moderated by youth race/ethnicity and socioeconomic status (SES). In 2013, objectively measured height and weight were collected for all 3rd–5th grade youth (n = 13.469) in a southeastern US county to determine body mass index (BMI) percentiles. Enumeration and audits of the county's parks (n = 103) were concurrently conducted. Neighborhood park and playground availability were calculated as the number of each facility within or intersecting each youth's Census block group. Multilevel linear regression models were utilized to examine study objectives. For boys, no main effects were detected; however, SES moderated associations such that higher park availability was associated with lower BMI percentile for low-SES youth but higher BMI percentile for high-SES youth. For girls, the number of parks and playgrounds were significantly associated with lower BMI (b = − 2.2, b = − 1.1, p < 0.05, respectively) and race/ethnicity and SES moderated associations between playground availability and BMI percentile. Higher playground availability was associated with lower BMI percentile for White and high-SES girls but higher BMI percentile for African American and low-SES girls. Considerable variation was detected in associations between park and playground availability and youth obesity by SES and race/ethnicity, highlighting the importance of studying the intersection of these characteristics when exploring associations between built environment features and obesity.