Despite evidence showing that the intake of ultra-processed food has a negative impact on health, diet quality and dietary vitamin E, its impact on vitamin E nutritional status and breast milk remains unknown. This study aimed to assess the influence of the consumption of ultra-processed foods on vitamin E biomarkers of lactating women. A cross-sectional study was performed with 294 lactating women. Food consumption was obtained by 24-hour dietary recall and foods were grouped according to the NOVA classification. Levels of alpha-tocopherol were analyzed by High Performance Liquid Chromatography. Breast milk vitamin E (BMVE) adequacy was based on the quantity of the vitamin in the estimated intake volume. The Kruskal-Wallis test was used to compare the tertiles and linear regression to association between ultra-processed food consumption and biomarkers. Ultra-processed foods accounted for 16% of energy intake and vitamin E intakes by all women were considered low. Serum alpha-tocopherol was 26.55 (SD 7.98) µmol/L, 5% (n=11) showed inadequate vitamin E (<12µmol/L), and 78% had an inadequate BMVE content (< 4mg/780mL). The regression showed that a higher dietary share of ultra-processed foods was associated with lower concentrations of serum alpha-tocopherol (β=−0.168, CI=−0.047–0.010, p=0.003) and inadequate BMVE content (β=−0.144, CI=−0.505–0.063, p=0.012) (adjustment for income and maternal age). Thus, higher dietary shares of ultra-processed foods had an impact on vitamin E biomarkers, suggesting that inadequate dietary intake practices during lactation may reduce the supply of vitamin E to women and breast milk.