Canine parvoviral enteritis (CPE) is a highly contagious, acute viral disease that mainly affects young dogs and can lead to systemic inflammatory response syndrome (SIRS), sepsis, endotoxemia and even death. The study aimed to evaluate the diagnostic and prognostic potential of hematological indices such as MLR, NLR, PLR, PNR and SII in CPV-infected dogs with SIRS at first admission. The retrospective study was performed on 51 CPV-infected and 20 healthy dogs. MLR, NLR, PLR, PNR, and SII indices were determined and compared between groups. A receiver operating characteristic (ROC) curve analysis was carried out to determine thresholds of sensitivity and specificity for hematologic indices. NLR, PLR, and PNR were the best predictors for supporting a diagnosis of parvoviral enteritis, with AUC values of 0.685, 0.762, and 0.884, respectively. Moreover, PLR and PNR, with AUC values of 0.740 and 0.769, respectively, were the most suitable indices to determine the prognosis of dogs with parvoviral enteritis with SIRS. In conclusion, these indices can be used as potential indicators for predicting disease outcomes and supporting a diagnosis of CPV-infected dogs with SIRS at first admission.