Summary Background There is cumulative recognition that increases in the dietary share of ultra‐processed foods result in deterioration of the nutritional quality of the overall diet and adverse health outcomes. Objective The purpose of this study was to assess the consumption of ultra‐processed foods and to examine its association with added sugar content in the diet of US children aged 2 to 19 years. Methods We classified all food items according to the NOVA food classification system and looked at the consumption of ultra‐processed foods, measured as percentage of total energy intake. We assessed dietary added sugar content by estimating its contribution to total energy intake and the proportion of individuals with diets exceeding the recommended limit of 10% of total energy intake from added sugars. We also examined the proportion of those who surpassed twice that limit. Gaussian and Poisson regressions estimated the association between consumption of ultra‐processed foods and estimates of added sugar content. Results Ultra‐processed foods contributed to 65% of total energy intake and to 92% of energy from added sugars in the diet of US children. The mean percent energy provided by added sugars in the observed period was 14.3%. Most individuals (70.9%) had diets exceeding the recommended limit of added sugar (<10% of total energy intake), and 18.4% of the population had diets surpassing twice the recommended level (20% of total energy intake). A 5.5% point increase in the dietary share of ultra‐processed foods determined a 1 percentage point increase in the dietary content of added sugars, with stronger adjusted associations among younger children. Conclusions Public health efforts to reduce added sugars in the diet of US children must put greater emphasis on decreasing the consumption of ultra‐processed foods.