BackgroundBreast cancer is associated with alterations in lipid metabolism. The treatment of breast cancer can also affect serum lipid composition. The purpose of this study was the examination of serum fatty acids (FAs) profiles in breast cancer survivors to assess if the FA levels normalize.MethodsSerum levels of FAs were determined by gas chromatography–mass spectrometry in a group of breast cancer patients at baseline (before treatment,n= 28), at two follow-up visits at 12 months (n= 27) and 24 months (n= 19) after the breast cancer resection, and in the group of healthy controls (n= 25). Multivariate analysis was performed to assess how FA serum profile changes following treatment.ResultsBreast cancer patients’ serum FA profiles at follow-ups did not normalize to the levels of control group. The greatest differences were found for levels of branched-chain (BCFA), odd-chain (OCFA) and polyunsaturated (PUFAs) FAs, all of which were significantly increased 12 months after the surgery.ConclusionsAfter treatment for breast cancer, the patients’ serum FA profile differs from the profile before treatment and from controls, especially 12 months after treatment. Some changes may be beneficial – increased BCFA and OCFA levels, and improved n-6/n-3 PUFA ratio. This may reflect lifestyle changes in breast cancer survivors and have an impact on the risk of recurrence.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12885-023-10914-2.