Background: Tooth resorption (TR) is a prevalent dental condition with under-investigated systemic implications, particularly regarding renal health. This study aimed to evaluate renal biomarkers, specifically symmetric dimethylarginine (SDMA), and the association between TR and blood parameters. Methods: Thirty-six cats (24 TR; 12 controls) were evaluated via intraoral radiography and blood analysis. Multivariable logistic regression was performed to identify independent predictors for TR, adjusting for age and sex. Results: Tooth resorption was diagnosed in 66.7% of the cats, predominantly affecting the mandibular first molars (409) and fourth premolars (108). A strong association was identified between TR stages and lesion types (p < 0.001). Cats with TR exhibited significantly higher serum SDMA concentrations (p = 0.011) and significantly lower albumin levels (p < 0.001) compared to controls. Hematological analysis revealed marked leukocytosis and monocytosis (p < 0.001) in the TR group. Most importantly, multivariable logistic regression identified SDMA as a predictor with TR presence (p = 0.012), with each unit increase in SDMA associated with a 3.5-fold increase in the likelihood of having resorptive lesions, independent of age and sex. Conclusions: Our findings regarding the oral-renal axis emphasize that feline TR involves chronic systemic inflammation. Consequently, it should be managed as a condition with measurable systemic impacts rather than merely a localized disease.