Accurate dietary assessment is essential for informing public health strategies, especially in culturally and linguistically diverse populations. South Asian (SA) migrants the second largest and one of the fastest-growing migrant groups in Australia experience a significantly higher burden of diet-related chronic conditions, including type 2 diabetes and cardiovascular disease(1). Despite this, their dietary behaviours remain underrepresented in national data and nutrition surveillance. Compounding this issue are unique cultural food practices, varied levels of dietary acculturation, and limited access to validated dietary assessment tools that reflect traditional eating patterns(2). The Australian Eating Survey Food Frequency Questionnaire (AES-FFQ) is a commonly used tool in Australian dietary research and clinical practice. However, its validity in culturally diverse populations such as SA migrants has not been evaluated. This study aimed to assess the comparative validity of the AES-FFQ in estimating macro- and micronutrient intakes in SA adults living in Australia, using a three-day weighed food record (WFR) as the reference method. A cross-sectional validation study was conducted among SA adults residing in Victoria, Australia. Participants completed both the AES-FFQ and a three-day WFR. Nutrient intakes from both tools were compared using paired t-tests or Wilcoxon signed-rank tests for group-level differences, and Pearson or Spearman correlations to assess associations. Bland-Altman analyses were used to evaluate individual-level agreement and systematic bias. Participants also completed a structured feedback survey exploring the acceptability and cultural relevance of the AES-FFQ. Of the 218 individuals who completed initial screening, 21 participants completed both the AES-FFQ and WFR. Moderate correlations were found for protein (r = 0.490, p = 0.024), niacin, vitamin B12, and beta-carotene, indicating acceptable agreement for some nutrients. However, intakes of energy (–953.2 kcal), total fat (–12.55 g), saturated fat (–4.54 g), sodium (–1476.46 mg), and added sugars ( –16.1 g) were significantly underestimated by the AES-FFQ compared to the WFR. Bland-Altman plots revealed wide limits of agreement and systematic underreporting, particularly for energy and sodium. Participant feedback reinforced these findings, with 85.7% reporting that the AES-FFQ did not reflect their typical dietary intake due to a lack of culturally specific food items and portion sizes. This study is one of the first to evaluate the AES-FFQ in a South Asian migrant population and highlights critical limitations in its use for this group. The findings support the urgent need to develop culturally tailored dietary assessment tools that better reflect the food practices of SA Australians. Doing so will improve the accuracy of dietary data and support more equitable and effective public health nutrition policies.