Pyometra is the most prevalent reproductive disorder threatens dogs and cats’ life. This study aimed to address the relation between pyometra, and oxidative stress and hormonal milieu. Bitches (n= 200) and queen (n= 281) admitted to veterinary clinics from which ten animals per each were pyometric. Health examination, ultrasound investigation and blood sampling were accomplished, besides histopathology of uterus in animals underwent elective ovariohysterectomy. The separated sera were assayed for inflammatory marker (C-reactive protein; CRP), oxidative stress biomarkers (glutathione peroxidase (GPX), catalase (CAT), total antioxidant capacity (TAC), nitric oxide (NO), superoxide dismutase (SOD), lipid peroxidation (MDA)), and hormones (progesterone (P4), estrogen (E2)). Animals with pyometra showed fever, polydipsia, polyuria, vomiting and purulent vulvar discharge. Ultrasound examination revealed the presence of anechoic to hypoechoic uterine fluid with an increased wall thickness. There was a significant increase in CRP (P< 0.01 and 0.05), NO (P< 0.05), MDA (P