Clinical courses of primary immune-mediated hemolytic anemia (pIMHA) in dogs are highly variable, however, limited information is available to predict their accurate prognoses. To evaluate the prognostic significance of clinical factors and to propose a scoring system to predict prognoses, the medical records of seventy-one dogs with pIMHA were reviewed. Overall mortality rate of dogs with pIMHA was 39% and most of the dogs died within 3 months from diagnosis. Sex, body weight, seasonality, packed corpuscular volume (PCV), platelet count (PLT), total plasma protein (TP), blood urea nitrogen, albumin, total bilirubin, sodium ion, prothrombin time, and fibrin/fibrinogen degradation products before immunosuppressive treatment can influence on survival time in dogs with pIMHA. A prognostic scoring system using a combination of sex, seasonality, PCV, PLT and TP can be statistically significant for raising the accuracy of prognostic prediction. Using the scoring system for prognostication in dogs with pIMHA may enable veterinarians to predict a prognosis easily and accurately.