To validate the Block98 food frequency questionnaire (FFQ) for estimating antioxidant, methyl-nutrient and polyunsaturated fatty acids (PUFA) intakes in a pregnant sample of ethnic/racial minority women in the United States (US). Participants (n = 42) were from the Programming of Intergenerational Stress Mechanisms study. Total micronutrient intakes from food and supplements was ascertained using the modified Block98 FFQ and two 24-h dietary recalls collected at random on nonconsecutive days subsequent to completion of the FFQ in mid-pregnancy. Correlation coefficients (r) corrected for attenuation from within-person variation in the recalls were calculated for antioxidants (n = 7), methyl-nutrients (n = 8), and PUFAs (n = 2). The sample was largely ethnic minorities (38 % Black, 33 % Hispanic) with 21 % being foreign born and 41 % having less than or equal to a high school degree. Significant and adequate deattenuated correlations (r ≥ 0.40) for total dietary intakes of antioxidants were observed for vitamin C, vitamin E, magnesium, and zinc. Reasonable deattenuated correlations were also observed for methyl-nutrient intakes of vitamin B6, betaine, iron, and n:6 PUFAs; however, they did not reach significance. Most women were classified into the same or adjacent quartiles (≥70 %) for total (dietary + supplements) estimates of antioxidants (5 out of 7) and methyl-nutrients (4 out of 5). The Block98 FFQ is an appropriate dietary method for evaluating antioxidants in pregnant ethnic/minorities in the US; it may be less efficient in measuring methyl-nutrient and PUFA intakes.