IMPORTANCE Eating meals, particularly dinner, with family members has been associated with improved dietary intake among youths. However, existing studies have not examined how family functioning may moderate or confound this association. OBJECTIVE To examine whether level of family functioning is associated cross-sectionally with frequency of family dinners and dietary intake among a US national sample of adolescents and young adults. DESIGN, SETTING, AND PARTICIPANTS Data from the 2011 questionnaire in the Growing Up Today Study 2 were used for this cross-sectional study. Linear regression models examined the extent to which family dinner frequency was associated with self-reported intake of fruits and vegetables, sugar-sweetened beverages, fast food, and takeout food among 2728 adolescents and young adults (age, 14-24 years). To explore effect modification by family functioning, an interaction term for family functioning and family dinner frequency was included for each dietary outcome. To explore confounding, models adjusted for family functioning were run. All models were stratified by sex and included participant age, educational attainment of mother's spouse or partner, and family structure as covariates. Statistical analysis was conducted between January 1, 2017, and August 31, 2018. MAIN OUTCOMES AND MEASURES Dietary intake measured by consumption of fruits and vegetables, sugar-sweetened beverages, takeout food, and fast food; family dinner frequency per week; and family functioning. RESULTS Among the 2728 participants, there were 1559 female and 1169 male participants who were 14 to 24 years of age (mean [SD] age, 19.4 [1.9] years) and were living with their parents in 2011. Most participants (2453 of 2649 [92.6%]) identified as white. More frequent family dinners were associated with higher-quality dietary intake regardless of level of family functioning; interactions between family functioning and family dinner frequency were not significant. Associations between family meal frequency and dietary intake outcomes did not change substantively when adjusting for family functioning. In adjusted models, more frequent family dinners were associated with higher intakes of fruits (female participants: