Diabesity-obesity and type 2 diabetes mellitus (T2DM)-has a profound effect on oral health, and modulation of the oral immune system may help in managing it. This review aims to elucidate the complex interconnection between diabesity, oral immunity, and oral health consequences. Diabesity affects metabolic homeostasis, leading to changes in the immune system within the oral cavity, and increases the incidence of chronic low-grade inflammation and oral diseases. Alterations in the oral microbiome and the breakdown of immune homeostasis further contribute to oral health problems. The reciprocal relationship between diabesity and oral diseases and how inflammation in the oral cavity can worsen systemic metabolic diseases are also described. Apart from periodontal diseases, diabesity increases susceptibility to dental caries, xerostomia, and oral mucosal lesions. Novel treatment strategies are presented with special emphasis on nutrition, lifestyle changes, new drugs, and immunomodulating therapies. The possibility of using a personalized medicine approach in the prevention and treatment of oral diseases in diabesity patients is discussed with regard to genetic and epigenetic factors, biomarkers, and genetic profiles. A combined strategy focusing on both systemic metabolic and oral immunomodulation is recommended to advance the knowledge of diabesity in oral health and thus improve the oral health and quality of life (QoL) of patients with diabesity.