Feline stomatitis or gingivostomatitis is a chronic inflammatory condition affecting approximately 0.7% of patients. The cause is multifactorial, involving infectious agents, genetic factors, and environmental influences. Therapeutic strategies include pharmacological and surgical interventions to controlling inflammation and enhancing patient quality of life. There are discussions in the literature regarding the potential involvement of adverse food reactions as a contributing factor to oral cavity lesions, without clear evidence. This case report describes the control of gingivostomatitis with a hypoallergenic diet in a cat that had oral lesions and who was refractory to conventional treatment with prednisolone and cyclosporine, even after periodontal treatment and partial tooth extraction. After 30 days of dietary change, there was complete remission of the lesions. The animal was then re-exposed to the previous food, with new lesions appearing after 7 days. Upon returning to the hypoallergenic food, there was new remission of the lesions. This report suggests that food sensitivity may play a role in the control of feline gingivostomatitis, as periods of hypoallergenic diet coincided with the remission of the condition, even without changes in medication. It reinforces the importance of investigating adverse food reactions as clinical signs in the oral cavity of cats.