A multicystic mass of the lung was found in a male 11-week-old Wistar Hannover GALAS rat. The cystic mass was located in the region of the right caudal lobe and had no direct communication with the tracheobranchial tree. Histologically, the pulmonary mass was composed of variably sized cysts containing mucinous material, cellular debris, erythrocytes, and inflammatory cells. In the septal stroma between the cysts, well-developed elastic and muscular arteries were present and in some areas, ectopic pancreatic tissue was observed. In the rest of the lung lobes, there was no evidence of previous pneumonic events or other respiratory diseases. Based on these findings, the present case was diagnosed as a congenital pulmonary sequestration with ectopic pancreatic tissue.