MYXOMATOUS MİTRAL VALVE DİSEASE (MMVD) is the most common cause of left-sided congestive heart failure (CHF) in dogs and is characterised by a chronic progression. The Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been proposed as promising inflammatory markers of various heart diseases in humans. Nevertheless, there is limited research on these parameters in dogs with MMVD. The study aimed to evaluate the clinical and diagnostic role of the NLR and PLR in dogs with various degrees of MMVD. This study included 15 healthy dogs and 60 dogs with MMVD classified based on the American College of Veterinary Internal Medicine (ACVIM) guidelines (Stage A-D). Complete blood count variables were determined for all dogs. NLR and PLR were calculated using the neutrophil, platelet, and lymphocyte counts. Stage D (with CHF) had significantly higher WBC, neutrophil count, NLR and PLR values than healthy dogs and other ACVIM stages. The degree of MMVD positively correlated with NLR and PLR. The best cut-off value of NLR to predict CHF was 6.84 with 81.12% sensitivity and 75.51%, and the best cut-off value of PLR to predict CHF was 280.80 with 63.64% sensitivity and 83.67%. In conclusion, the NLR and PLR could be used to determine the inflammatory state in dogs with MMVD. Also, both parameters may be a valuable aid to other conventional diagnostic methods for predicting CHF.