Objective: To determine the effect of electro-acupuncture (EA) treatment on serum levels of interferon-γ (IFN-γ) in rats with 7,12-dimethylbenz(α)anthracene (DMBA)-induced breast tumors. Methods: Twenty five female Wistar rats were divided randomly into 5 groups: normal group (N; neither DMBA-induced nor treated with EA); control group (C; DMBA-induced only); EA 3 days : (DMBA-induced + EA for 3 days); EA 5 days: (DMBA-induced + EA for 5 days); EA 10 days: (DMBA-induced + EA for 10 days) group. Animals were acclimatized from day 1 to day 7. Subcutaneus injections of DMBA 10mg/kg BW was administered every second day, from days 7 to 35. Acupuncture was performed every second day from day 42. Rats were sacrificed on the second day after the last acupuncture, breast tumors excised and stained histological sections were analysed by light microscopy. At sacrifice, blood was extracted from the heart for measurement of serum IFN-γ by ELISA. Results: All of the DMBA-induced rats developed tumors. Electro-acupuncture significantly increased IFN-γ levels in DMBA induced rats, when compared to control group. Conclusions: Our findings suggest that EA significantly increases IFN-γ levels in DMBA-induced breast tumors.