Objective: To determine sociodemographic correlates of contemporary screen time use among a diverse population-based sample of 9- and 10-year-old children. Study design: In 2021, we analyzed cross-sectional baseline (2016-2018) data from the Adolescent Brain Cognitive Development study (n = 10 755). Multiple linear regression analyses were conducted to estimate associations between sociodemographic factors (sex, race/ethnicity, country of birth, household income, parental education) and 6 contemporary forms of screen time (television, videos [eg, YouTube], video games, social networking, texting, and video chat). Results: On average, children reported 3.99 hours of screen time per day across 6 modalities, with the most time spent watching/streaming television shows/movies (1.31 hours), playing video games (1.06 hours), and watching/streaming videos (1.05 hours). On average, Black children reported 1.58 more hours of screen time per day and Asian children reported 0.35 less hours of screen time per day compared with White children (mean 3.46 hours per day), and these trends persisted across most modalities. Boys reported higher overall screen time (0.75 hours more) than girls, which was primarily attributed to video games and videos. Girls reported more time texting, social networking, and video chatting than boys. Higher income was associated with lower screen time usage across all modalities except video chat. However, in high-income households, Latinx children reported 0.65 more hours of screen time per day than White children. Conclusions: Given the sociodemographic differences in child screen use, guideline implementation strategies can focus on key populations, encourage targeted counseling by pediatricians, and adapt Family Media Use Plans for diverse backgrounds.