Accessory spleens are one or more areas of normal ectopic splenic tissue of variable size supplied by the branches of the splenic artery. A 7 year-old mixed breed male dog was fixed for use as a model in anatomy hall. During the abdominal dissection, the gross examination showed a 6.3×3.1×1 cm mass that was situated on the caudodorsal border of the spleen. Its appearance and firm consistency were similar to those of spleen. There was no connection between the spleen and this mass. It was supplied by accessory splenic artery. Microscopic examination of the mass revealed some structures similar to spleen.