To assess adherence to the 2015-2020 Dietary Guidelines for Americans and 2018 Physical Activity Guidelines, and identify sociodemographic predictors of adherence among children. Cross sectional. Colorado, United States. Children aged 5 (n = 482). Sex, race/ethnicity, maternal education, maternal employment, maternal subjective social status and household income were assessed via questionnaires. Diet was assessed via 2 interviewer-administered 24-hour dietary recalls. Physical activity was objectively-measured with accelerometry for 7 days. Adherence was defined as a Healthy Eating Index-2015 score of ≥70 and/or ≥6 hours/day of light, moderate and vigorous activity. For each predictor, logistic regression was used to estimate odds ratios for adherence to the diet guidelines only, the activity guidelines only or both guidelines. In the full sample, 29% of children were non-adherent to both guidelines, 6% adhered to the dietary guidelines only, 50% adhered to the activity guidelines only and 14% adhered to both. Girls had a 41% lower odds of adhering to the physical activity guidelines than boys (p = 0.01), after adjustment for race/ethnicity, household income and maternal education level, perceived social status and employment status. Efforts to improve the health of young children should promote adherence to the Dietary Guidelines for Americans among all children. Targeted interventions that increase physical activity among girls may help to mitigate health disparities.