Background: Breast cancer has become a major public health problem in developing regions, asrnincidence rate is particularly growing in these regions of the world. Oxidative damage andrnmodification of biomolecules including proteins, lipids and DNA can increase the risk ofrnmutagenesis. It has also been suggested to play an important role in breast carcinogenesis, andrnprogression of the disease.rnObjective: The aim of this study was to investigate the serum markers of oxidative stress amongrnbreast cancer patients in Tikur Anbesa specialized teaching hospital, Addis Ababa, Ethiopia.rnMethods: The comparative cross sectional study was conducted on a total of 119 studyrnparticipants (95 breast cancer patients and 24 female controls without malignancy). Breast cancerrnpatients were classified based on their clinical stages at diagnosis (stage I, II, III and IV).Thernparameters measured were serum levels of malondialdehyde (MDA), protein carbonyl, reducedrnglutathione (GSH) , total antioxidant capacity (TAC), uric acid, and albumin using their standardrnmethods. Data analyses were done with SPSS version 21 system.rnResults: The present study result demonstrated that there were statistically significantly higherrnserum MDA and protein carbonyl levels in breast cancer group than in control group while thernlevels of TAC, GSH, albumin and uric acid were decreased (p-value < 0.05). Patients with thernhighest mean serum MDA and median protein carbonyl levels were those with stages III and IVrnas compared stages I and II (p-value < 0.05). Among the case groups, as breast cancer progressesrnto a higher stages, the levels of MDA, protein carbonyl, TAC and albumin were found tornincrease (p < 0.05). We also found significant decrease in the mean levels of GSH in stage IV asrncompared to other stage (p < 0.05). Moreover, a negative correlation was observed betweenrnserum levels of GSH versus serum levels MDA and protein carbonyl.rnConclusion: Breast cancer patients suffer a high degree of oxidative stress which is associatedrnwith decrease in TAC and GSH levels as well as significant degree of lipid peroxidation andrnprotein oxidation. Clinical stages of breast cancer were associated with oxidative stress. Thernoxidative and antioxidant markers showed a negative correlation in patients with breast cancer.rnKey words: Breast cancer, serum marker, oxidative stress