Abstract Introduction In dogs, the most frequent tonsillar lesions are tonsillitis, lymphoid hyperplasia and malignant neoplasms, especially squamous cell carcinoma and lymphoma. Benign tonsillar proliferations such as inflammatory polyps are uncommon. In man, several benign and malignant lesions of tonsils are reported, including a rare entity, the lymphangiectatic fibrous polyp. We report a case of a single tonsillar polyp in a 13-year-old female Bichon dog with moderate inspiratory dyspnoea associated with a pedunculated pink mass growing from the left palatine tonsil and partially obstructing the pharyngeal lumen. Materials and Methods Tissue specimens were prepared for histology by standard protocols. Immunohistochemistry was performed using the streptavidin-biotin-complex method and anti-human LYVE-1 and CD3 antibodies. Results Histologically, the polyp was covered by a non-keratinized pluristratified squamous epithelium and was formed by several lymphoid follicles and a central core of numerous severely ectatic lymphatic vessels. Endothelial cells lining the dilated vessels labelled positively for LYVE-1, an antigen specific for lymphatic endothelial cells. Conclusions We describe a case of an unusual tonsillar polyp in a dog sharing strong clinical and histological similarities with the rare human lymphangiectatic fibrous polyp.