Ovine pulmonary adenocarcinoma is a naturally occurring retrovirus-induced contagious lung neoplasm in sheep. The current report aims to describe clinical and histopathological characteristics of the disease in an Egyptian sheep farm. In which, 4 dead and 5 sick young sheep were subjected to clinical, gross and histopathological examinations. For histopathological examination, tissue specimens were taken from lungs, mediastinal lymph nodes, liver, heart, kidneys and brain, fixed in 10% neutral buffered formalin and processed for light microscopy. Examined animals showed release of copious amount of mucoid fluid from their nostrils and marked loss of body weight. At necropsy, there were many solid grayish nodules exuding frothy fluid in the lungs and accumulation of mucoid fluid in the pleural cavity. Histopathological examination revealed presence of many nonencapsulated neoplastic foci originating from the alveolar epithelial lining. Neoplastic foci consisted of cuboidal and columnar cells that arranged in papillary and acinar forms. Proliferating cells appeared supported by loose connective tissue containing some fibroblasts and small blood vessels. Prominently, there was large number of swollen and ruffled macrophages in alveolar spaces adjacent to neoplastic foci. In conclusions, release of copious amount of mucoid fluid from nostrils and transformation of alveolar epithelial lining into cuboidal and columnar cells are pathognomonic for ovine pulmonary adenocarcinoma.