Background: Sarcina spp is a Gram-positive, coccoid microorganism which forms tetrads or octets, and is observed with a characteristic "bundle" arrangement. The most recognized species are Sarcina ventriculi and Sarcina maxima. It has been described as part of the normal microbiota in horses and cats, but it has also been linked to abomasal bloat in goats, lambs, and calves, although its causality has not been proven yet. Case description: This work presents the case of a 3-months-old female horse which died of generalized tympanism. Macroscopic findings showed mild cyanosis and abundant gas in the lumen of the stomach, small and large bowel. Microscopically, high numbers of Gram-positive microorganisms compatible with Sarcina spp. in the gastric lumen and on the surface of the small and large bowel were observed, along with mild inflammation. Conclusion: The severe tympanism was the only relevant lesion observed and could explain the death of the animal. Although it is not possible to determine a relationship between these lesions and Sarcina spp, it is interesting to highlight that the high amount of these bacteria could be associated with gas production and tympanism. It is important to continue investigating the role of Sarcina spp. in horses, and its possible link with tympanism.