Purpose: This study is aimed at evaluating the relationship between dietary and serum advanced glycation end-products (AGEs) with serum inflammatory and oxidative stress biomarkers in breast cancer (BC). Methods: A sample of BC patients was followed for 12 months (March 2020–January 2022). Three-day food consumption record and serum samples were taken before surgery (T1), before chemotherapy (T2), at the 6th month of chemotherapy (T3), and at the 12th month of chemotherapy (T4). Dietary AGE intake was represented by carboxymethyl lysine (dCML). Serum levels of CML, inflammation, and oxidation biomarkers were determined with biochemical blood tests. The results were compared according to human epidermal growth factor receptor-2 (HER2) status. Results: Thirty-two women with BC and 32 age and body mass index-matched healthy women participated. No significant correlation was found between dCML and serum CML, inflammatory or oxidative stress biomarkers at T1, T2, and T4. A weak positive correlation was demonstrated between dCML and serum malondialdehyde levels (rho=0.355, p=0.046) at T3. The serum CML, inflammation, and oxidation biomarker levels of the HER2− group were significantly higher than those of the HER2+ group at T1. Conclusion: This study suggests that there is limited correlation between dCML and serum inflammation and oxidative stress biomarkers in BC patients. Inflammation and oxidative biomarker levels appear to decline with treatment although dietary and serum AGE levels show not a corresponding significant decline. The HER2− subtype appears to be associated with higher dietary and serum AGEs and higher inflammatory and oxidative stress biomarkers.