ContentsNumerous studies reported an increase of oxidative stress increases in both women and female laboratory animals after ovariectomy. However, there is little information about the evaluation of antioxidative/oxidative status in ovariectomized dogs. The purpose of this study was to examine the changes in oxidative stress markers after ovariohysterectomy (OHE) in female dogs. The study included eighteen healthy mongrel female dogs. Blood samples were collected immediately before surgery and 14 and 30 days after surgery. Following parameters of oxidative stress intensity were determined: the erythrocyte activity of glutathione peroxidase (GSH‐Px) and superoxide dismutase (SOD) as well as the plasma concentrations of thiobarbituric acid reactive substances (TBARS), radical cations of N,N, diethylpara‐phenylene diamine (RC‐DEPPD), sulfhydryl groups (SHgroups), bityrosine and formylkynurenine. The activity ofGSH‐Px increased markedly, although not significantly, 14 days afterOHEand then significantly decreased at 30 days afterOHE. A significant increase in plasmaTBARS, bityrosine and formylkynurenine concentrations and a decrease inSHgroup content were concurrently noted at 30 days after surgery. Acquired results suggested that a loss of control overROSproduction occurred in female dogs afterOHE, which could lead to oxidative stress in the late post‐operative period. In conclusion, our findings indicated thatOHEis related with the risk of oxidative stress in the late period after operations. Given that oxidative stress contributes to the pathogenesis of various diseases, this may suggest an increased risk of disorders in ovariectomized female dogs; however, further studies are necessary to confirm this hypothesis.