Mastitis is a rare condition that can be diagnosed in female cats of all breeds and ages. It is usually caused by bacterial agents and is frequently encountered secondarily in feline mammary fibroepithelial hyperplasia (FEH). If left untreated, it can peril both the queen and her kittens. Therefore, a reliable and quick diagnosis is the primary key to successful treatment. Conventional diagnosis consists of a clinical and ultrasound evaluation of the queen’s mammary glands. However, there is a lack of literature specifically focused on mastitis in queens. Consequently, the present review brings forth the existing knowledge regarding mammary gland inflammations in cats, with the goal of improving current clinical evaluation and treatment plans.