A 9 yr old castrated male mixed-breed dog was presented for acute vomiting. Abdominal radiographs appeared to show a normal positioned stomach with marked gas dilation, which persisted despite frequent suctioning with a nasogastric tube. An abdominal ultrasound showed splenomegaly, malpositioning of the spleen, and the pyloroduodenal junction. A ventral midline celiotomy revealed an organoaxial gastric volvulus, rotating on the gastroesophageal, and pyloroduodenal junctions. The omentum was not overlying the stomach, typically seen in mesenteroaxial gastric volvulus. The body of the stomach was derotated with no evidence of gastric necrosis noted. The spleen was in the right cranial abdomen and returned to its normal anatomic position after derotation of the stomach. The patient recovered uneventfully and was discharged the next day. To the authors’ knowledge, organoaxial gastric volvulus has not been reported in dogs. This is rare in humans but occurs most commonly in children <5 yr of age associated with hernias. The recommended treatment is surgical in majority of cases. As a result of the unusual orientation of the stomach, the diagnosis of gastric dilatation-volvulus was challenging. Organoaxial gastric volvulus demonstrates the need for further imaging and evaluation in cases of persistent gas dilation.