High-fat food intake is associated with atopic dermatitis (AD), but the role of habitual dietary habits related to the frequency of high-fat food intake remains unclear. To address this, we developed a frequency-based dietary index, Diet Quality based on Dietary Fat Score, to assess high-fat food intake and examined its association with AD in 13 561 young Chinese adults (mean age = 22·51 years, (sd 5·90)) from Singapore and Malaysia. Using an investigator-administered questionnaire aligned with the validated International Study of Asthma and Allergies in Childhood protocol, we conducted multivariable logistic regression analysis, adjusting for demographics, body mass index, genetic predisposition and lifestyle factors, with false discovery rate correction for multiple comparisons. Frequent high-fat food intake was associated with higher odds of AD (adjusted OR (AOR): 1·53; 95 % CI: 1·31, 1·77; < 0·001). The association remained significant regardless of total fat intake (AOR: 1·45; 95 % CI: 1·05, 1·80; < 0·001) and among individuals with high fruit and vegetable intake (AOR: 1·49; 95 % CI: 1·19, 1·86; < 0·001) or low energy intake (AOR: 1·40; 95 % CI: 1·05, 1·86; < 0·05). No synergistic effects were observed between dietary factors. These findings highlight that frequent intake of high-fat foods is independently associated with AD, emphasising the potential of dietary moderation in AD risk management.