A 2-month-old female Birman cat was brought for evaluation of a small mass protruding from the anterior surface of the conjunctiva of the third eyelid of the right eye. The initial ophthalmic examination did not reveal any other obvious clinical signs. Given that the mass doubled in diameter in just 3 weeks, it was surgically removed and subjected to histopathological analysis. The definitive diagnosis was a conjunctival dermoid. To the authors’ knowledge, this is the first case of a primary dermoid on the conjunctiva of the third eyelid described in a Birman cat.