Three cats with 2 weeks to 1 month history of drooling, halitosis, difficulty eating and pain on opening the mouth were presented to local animal hospitals. On physical examination, the gingiva was swollen, bright red and very painful with bilaterally symmetric pattern. Surgically excised abnormal gingival biopsy samples were requested for diagnosis. Histopathologically, gingival epithelium showed severe hyperplasia and ballooning degeneration. Moderate to severe infiltration of lymphocytes and plasma cells were presented in lamina propria. Immunohistochemically, inflammatory cells of the samples demonstrated major positive reactions for T lymphocytes. But some plasma cells also presented. According to polymerase chain reaction, tissues samples were negative for four kinds of feline viral pathogens. Based on the clinical, gross, histopathologic findings, these three cases were diagnosed as lymphoplasmacytic gingivitis in cats. In our best knowledge, this is the first case report in Korea.