Background: Constructs based on Social Cognitive Theory have shown utility in understanding dietary behavior; however, little research has examined these relations in youth and parents concurrently. Unique demands of dietary management among families of youth with type 1 diabetes (T1D) suggest the importance of investigation in this population. The purpose of this study was to develop and evaluate youth and parent measures of self-efficacy, outcome expectations, and barriers for healthful eating, and parent modeling of healthful eating, in a sample of youth with type 1 diabetes and their parents. Methods: Youth (n=252) ages 8–18 years with diabetes duration ≥1 year and parents completed self-report measures of healthful eating attitudes including self-efficacy, perceived barriers, positive and negative outcome expectations; youth reported parent modeling of healthful eating. Youth dietary intake from 3-day diet records was used to calculate the Healthy Eating Index 2005 and the Nutrient Rich Foods 9.3 index, measures of overall diet quality. The relations among parent and youth healthful eating attitudes, parent modeling, and youth diet quality were examined using structural equation modeling. Results: Internal consistency and test-retest reliability of the measures were acceptable. The structural equation model demonstrated acceptable fit (CFI/TLI=0.94/0.94; RMSEA=0.03), and items loaded the hypothesized factors. Parent modeling β ^ = .27 , p = .02 and attitudes toward healthful eating (latent variable comprised of self-efficacy, barriers, outcome expectations) β ^ = .16 , p = .04 had direct effects on youth diet quality. Parent modeling had a direct effect on youth attitudes β ^ = .49 , p < .001 ; parent attitudes had an indirect effect on youth attitudes through parent modeling β ^ = .12 , p , < .001 . Youth attitudes were not associated with youth diet quality. Overall, the model accounted for 20% of the variance in child diet quality. Conclusions: Parent diet-related behaviors demonstrated an impact on youth attitudes and diet quality, suggesting the importance of family-based clinical and public health efforts to improve diet.