A reliable diet quality (DQ) assessment is critical to empower individuals to improve their dietary choices. Controversies persist as to whether self-perceived DQ is accurate and correlated with actual DQ as assessed by validated nutrient intake indexes. We used National Health and Nutrition Examination Surveys data to examine whether a higher self-perceived DQ was positively associated with a more optimal nutrient intake as reflected by the Food Nutrient Index (FNI) and Diet Quality Score (DQS). Comparative analyses were performed for three self-perceived DQ groups: (I) “excellent or very good” DQ, (II) “good or fair” DQ, and (III) “poor” DQ. The FNI and DQS differed substantially across groups and sexes. FNI scores ranged from 65 to 69 in participants with a self-reported excellent or very good DQ, whereas participants with a self-perceived poor DQ scored significantly lower (53–59). We also observed age- and sex-specific patterns, with the lowest overall FNI scores found in males aged 18–30 years and females aged 31–50 years. DQ intergroup differences were more pronounced in females than in males. Our findings suggest that higher self-perceived DQ is associated with a more optimal nutrient intake and indicate potential helpfulness of self-perceived DQ as a quick and still underexplored indicator with intrinsic limitations.