Summary The authors present the case of a five year old, male, lethargic pet guinea pig presented to the clinic with anorexia. The symptoms started the previous day. Physical examination revealed dyspnoe and tachycardia. A gas and fluid filled tense structure could be palpated in the abdomen, which was painful upon palpation and exacerbated the symptoms. Radiological examination suspected gastric dilatation and volvulus. During laparotomy the authors found gastric dilatation and a 180 degree rotation of the stomach, which was resolved. The small intestines, the colon and the caecum were pushed to the left side of the abdomen by the stomach. Parts of the small intestines were located in front of the stomach. The animal fully awoke from surgery but after 3 hours its status got worse and the animal died 5 hours after surgery. The owner took the animal home, so necropsy couldn’t be performed. No long term survival in a guinea pig with gastric volvulus has been reported in the literature.