BackgroundEvidence suggests dietary acculturation can increase obesity and chronic disease risks. However, acculturation effects on diet quality among subgroups of Hispanic Americans is not well studied. ObjectivesEstimating percentages of Hispanic Americans with low, moderate, and high acculturation using 2 proxy measures with different language variables was the first objective. Identifying similarities and dissimilarities in diet quality differences by acculturation level between Mexican Americans and other Hispanic Americans was the second objective. MethodsThe study sample included 1733 Mexican American and 1191 other Hispanic participants aged ≥16 y from National Health and Nutrition Examination Survey 2015–2018. Proxy measures included in the 2 acculturation scales were nativity/United States residence length, immigration age, language spoken at home (home), and language of dietary recall (recall). Replicate 24-h dietary recalls were conducted, and diet quality was assessed using the 2015 Healthy Eating Index. Analyses included statistical methods for complex survey designs. ResultsFor Mexican Americans, 8%, 35%, and 58% had low, moderate, and high acculturation on the home scale compared with 8%, 30%, and 62% on the recall scale. For other Hispanics, 17%, 39%, and 43% had low, moderate, and high acculturation on the home scale compared with 18%, 34%, and 48% on the recall scale. Similarities between ethnicities included higher acculturation associated with lower intakes of fruits, vegetables, total protein foods, seafood and plant proteins, and saturated fats and greater intake of sodium. Dissimilarities included higher acculturation associated with more whole grains and added sugars intakes and less refined grains intake (Mexican Americans), and less total dairy and fatty acids intakes (other Hispanic Americans). ConclusionsHigher acculturation is associated with worsening diet quality for fruits, vegetables, and protein foods in all Hispanic Americans. However, associations of higher acculturation with worsening diet quality for grains, added sugars, dairy, and fatty acids were present only in specific subgroups of Hispanic Americans.