Background:Previous studies have suggested an association between equine immune‐mediated hemolytic anemia and clostridial infections or neck abscesses.Objective:The purpose of this report was to describe and characterize the hematologic abnormalities in a horse withClostridium‐associated immune‐mediated hemolytic anemia. We also retrospectively evaluated hematologic abnormalities in 8 horses with clostridial myositis or subcutaneous emphysema.Methods:A 7‐year‐old Foreign Warm‐Blood gelding was evaluated for anemia and a cervical abscess. CBCs and reticulocyte counts were obtained using an Advia 120 analyzer and evaluation of Wright's‐stained smears. All cases of equineClostridiumspp. myositis or subcutaneous emphysema over a 7‐year period were identified in a retrospective search of the University of Minnesota Veterinary Teaching Hospital database. Clinical, hematologic, and microbiological findings were recorded.Results:Clostridium perfringensgenotype A was isolated from the neck wound of the gelding. The CBC was characterized by severe regenerative anemia, intravascular hemolysis, and RBC agglutination. A direct Coombs' test was positive. Moderate numbers of spheroechinocytes were observed. The total automated reticulocyte count was 4.5% (56,700/μL), with most reticulocytes having low absorbance (mature reticulocytes). The anemia responded to penicillin and steroidal and nonsteroidal immunosuppressive drugs. Of 8 horses with myositis, all of which involved the cervical region, 5 were anemic, 1 had a positive direct Coombs' test, and 2 had increased numbers of type III echinocytes and spheroechinocytes.Conclusions:The presence of type III echinocytes or spheroechinocytes may be helpful in diagnosing immune‐mediated hemolytic anemia associated with clostridial infections in horses. Automated reticulocyte counts may detect very low levels of reticulocytosis in hemolytic anemia in horses.