The aim of this study was to determine the antioxidant effect of the novel bee-product based intramammary formulation ApimastR on the oxidative status of dairy cows. ApimastR was administered intramammarily three times at 12 h intervals to 10 dairy cows on each of the three dairy farms. The oxidative status markers and some metabolic parameters were determined in the milk (GSH-Px, d-ROM, SOD, BAP, TAS) and in the serum (SOD, GSH-Px, NEFA, BHB, glucose). The results showed that the effect of ApimastR was mostly local, regardless of the concentration used (3% and 1%) as there was an increase in the concentration of GSH-Px and TAS in the milk, but not in the blood. It is also of a short-term nature since the values of these parameters were significantly lower 7 days after application. The expected connection between the increase of ROM in milk samples from the microbiologically positive quarters was not found. The results of this study confirm the local antioxidant effect of ApimastR in the udder, with implications for non-antibiotic subclinical mastitis treatment. Key words: mastitis; oxidative stress; ApimastR; propolis; dairy cows