Background: Mental disorders impose a significant health and economic burden on both developed and developing countries. The relationship between nutrition and mental disorders has become an important topic of interest in recent years. Therefore, identification of modifiable risk factors for anxiety is a serious and critical research imperative. Thus, this study aimed to evaluate the relationship between the “diet quality index international” (DQI-I) and anxiety as a major subject. Methods: This cross-sectional study was conducted on 194 men and women, who were randomly selected to perform the routine examinations before marriage. In this research, socio-demographic and anthropometric indicators, such a dietary intake1 and mental health were measured. To measure the former, a Food Frequency Questionnaire (FFQ) was applied and to determine the latter, a short version of the self-report depression, anxiety, and stress scale questionnaire (DASS-21) was used. Results: Univariate and multivariate linear regressions of anxiety and DQI score demonstrated significant association between DQI score and anxiety in all participants. A negative correlation was also seen between DQI score and anxiety in all participants. The anxiety scores reported for males and females did not introduce a significant difference. Adjustments for age, education, income, job, smoking, physical activity, and body mass index did not change the aforementioned associations. Conclusion: In this study, a significant association was observed between diet quality and the risk of mental disorders. The increase in DQI in participants caused a remarkable reduction in their level of anxiety. A healthy diet proved to be inversely associated with anxiety, while unhealthy dietary patterns were associated with increased risk of anxiety.