Cardiovascular disease is the leading cause of death in the United States and is estimated to affect 1 in 3 Americans. The Mediterranean diet has proved to be efficacious in preventing and treating cardiovascular disease. The purpose of this study was to determine how psychosocial determinants affect cardiac patient abilities to adhere to the Mediterranean diet. Secondly, I sought to determine if prior knowledge, a proximal determinant to the SCT constructs, and familiarity with the diet affect diet quality. The final purpose was to analyze if socioeconomic variables affect a cardiac patient's cognitive capabilities for diet adherence. I used social cognitive theory (SCT) for the theoretical framework. A cross-sectional pilot study of cardiac patients was conducted at a large outpatient cardiology hospital. The results showed that dietary adherence was associated with improvements in the SCT constructs. Likewise, participants reporting familiarity with the Mediterranean diet consumed diets that were 11% healthier, on average, than those whom were unfamiliar. Finally, household income was the only socioeconomic variable associated with improvements in the SCT constructs. In conclusion, social cognitive theory, specifically self-efficacy, self-regulation, and perceived expected outcomes, were highly predictive of diet quality in cardiac patients. Prior knowledge of the diet was also associated with diet patterns that closely matched the Mediterranean diet, indicating that patient education plays a key role in dietary adherence.