AbstractOne of the causes of pregnancy loss is pyometra, defined as an accumulation of purulent material in the uterine lumen. A 1‐year‐old, female Shih‐Tzu with a history of mating and no additional significant medical history, was presented with anorexia, pyrexia and vomiting for 4 days of duration. The female dog was clinically ill with abnormal laboratory findings. Transabdominal ultrasound revealed an embryo and gestational sac in the left uterine horn and large collection of hypoechoic fluid with echogenic particles in the right uterine horn. Based on these findings, a suspected diagnosis of pyometra or mucometra with pregnancy was made. Due to the severity of the animal's condition and the high risk of death, ovariohysterectomy was immediately recommended. After surgery, the existence of pyometra and gestational sac were confirmed by opening the right and left uterine horns. According to the rare occurrence of this condition, we reported this case.