Introduction: Nutrition is crucial in all stages of life, particularly during childhood and adolescence, when a diet that promotes neural growth is essential. Good nutrition provides proteins and micronutrients that are vital for cognitive development, whereas a deficient diet, high in ultra-processed foods rich in fats, sodium, and sugars, can be associated with reduced cognitive abilities. Worldwide, the consumption of ultra-processed foods is on the rise. Objective: To evaluate the association between dietary profile and performance in calculation, math fluency, and applied problems subtests of the Woodcock-Muñoz cognitive abilities test in Chilean schoolchildren aged 7 to 11. Materials and methods: Cross-sectional study based on data from the Third Longitudinal Survey of Early Childhood 2017, with a sample of 10.132 children aged 7 to 11. The Kruskal-Wallis nonparametric test was used to compare median scores on the subtests, distributed across three levels of dietary profile. Results: The average age was 9.4 years (SD = 1.2), with a similar distribution between sexes. Significant differences were observed in applied problems (p= 0.00010) and calculation (p = 0.00154), with lower scores in the group with a less healthy diet. No differences were observed in math fluency (p = 0.56300). Conclusions: A dietary profile low in healthy foods and high in ultra-processed items is associated with lower cognitive subtest scores, underscoring the need for educational strategies to improve dietary habits and cognitive development in Chilean children.