This study aimed to investigate the morphological patterns of the genital tract after long-term treatment of deslorelin acetate in a female cat, a gonadotropin-releasing hormone agonist currently used in adult cats to obtain transient oestrus suppression. A 1-year-old Chartreux female cat was treated with 4.7 mg deslorelin acetate to suppress oestrus manifestations. The treatment was repeated for a total of × 3 every 2 years. After 8 years, the female cat came into oestrus again, but she was no more implanted, and an ovariohysterectomy was performed. Before surgery, an ultrasound examination was performed that showed a normal uterus and the presence of about 5 follicles in ovaries. Concentrations of oestradiol, progesterone, and vaginal smears were compatible with oestrus. During surgery, a very short ovarian pedicle was observed yet neither uterus nor ovaries presented appreciable alterations. At histology, the ovaries presented a juvenile appearance with numerous primordial and periovulatory follicles. The uterus showed marked endometrial hyperplasia with polypoid projection and atrophic myometrium. Based on this case report, deslorelin acetate is a powerful drug able to preserve ovarian function. However, the suppression of gonadotrophin, especially for a long period, has a detrimental atrophic effect on the target organs during treatment and, on the opposite, hyperplastic changes may occur after the restoring of normal cyclicity.