Overweight and obesity have continued to increase among all age groups in the United States. The exact causes of overweight and obesity are still unspecified. Understanding factors affecting children’s eating behaviors may provide a unique insight into future interventions to prevent overweight and obesity. Guided by the theory of planned behavior (TPB), this dissertation aimed to 1) review factors in the literature affecting the eating behaviors of preschoolers, 2) determine the extent to which demographic characteristics and the primary caregivers’ factors (ie, beliefs, intention to provide a healthy diet, and feeding practices) can explain the variance in the diet quality of preschoolers, and 3) determine the extent to which demographic characteristics and the primary caregivers’ factors (ie, beliefs, intention to provide a healthy diet) can explain the variance in their feeding practices. Primary caregivers were defined as individuals responsible for the upbringing of a preschooler (eg, parent, grandparent, guardian, or older sibling). This dissertation consisted of 3 manuscripts. First, the review paper was to summarize, critically analyze, and synthesize the existing body of literature on the factors influencing the eating behaviors of preschool children according to their caregiver's determinants and identify the research gaps to guide future research studies. Two electronic databases were searched including PubMed and CINAHL Plus with Full Text, to identify eligible studies that were published between January 2017 and March 2022. A cross-sectional descriptive correlational design was used for the second and third manuscripts. Data were collected using self-administered surveys in REDCap and telephone interviews regarding diet quality. The participants were recruited from Facebook across the US and various settings and facilities in the Midwest. A total of 146 primary caregivers of preschoolers were recruited (88% mothers, 77% White, 77% married, average age 35 years, average education 16 years, and 82% with one child). The review paper of 10 studies indicated that most lacked solid theoretical grounding and emphasized descriptive findings rather than explanatory relationships. The results of the second paper indicated that about 16% of the variance in diet quality (DASH index score)[F (4.141)= 7.75, p<. 05] was explained by race and 3 feeding practices (restriction for health, restriction for weight control, and food as a reward) with being non-White and restricting foods for preschoolers for health reasons being the most strongly associated with poorer diet quality. Lastly, the findings from the third paper showed that various factors accounted for the variability in each of the 12 subscales of the comprehensive feeding practices. The amount of the variance explained in each of the 12 subscales ranged from 4% to 25%. This dissertation offers a new application of the Theory of Planned Behavior and provides preliminary data for future studies and areas for interventions aimed at improving the feeding practices of primary caregivers and diet quality in preschoolers.