For a study, researchers sought to understand that the cause of the self-limiting vasculitis known as Kawasaki disease (KD) remains uncertain. Breastfeeding has reportedly been linked to possible protection against the development of KD. However, it is yet unknown whether breastfeeding affects how coronary artery lesions (CALs) develop. The medical records of patients with KD as their primary diagnosis admitted to their hospital between May 2017 and November 2018 were retrospectively reviewed. Standardized telephone interviews were conducted to learn about dietary habits before the commencement of KD. About 293 (39.3%) were nursed partially, 223 (51.6%) were exclusively breastfed, and 52 (9.2%) were given formula. The characteristics of the three groups did not differ significantly in terms of age, gender, partial KD, intravenous immunoglobulin (IVIG) resistance, or laboratory factors. Even after correcting for confounders, patients who were exclusively or partially breastfed appeared to have a higher incidence of CALs than those who were fed formula, although these differences were not statistically significant. The results remained the same (P>0.05) when patients older than 6 months were divided into formula feeding, partial breastfeeding for less than 2 months, partial breastfeeding for more than equal to 2 and less than 4 months, partial breastfeeding for between more than equal to 4 and less than 6 months, and exclusively breastfeeding. The development of CALs in KD is not protected by breastfeeding.