Veterinarians will encounter hematologic abnormalities routinely while treating small animal cancer patients. Some of these abnormalities, such as monoclonal gammopathy, are relatively rare and highly associated with specific neoplasms. Thus, their detection should compel a search for underlying cancer. Other hematologic abnormalities, such as anemia or thrombocytopenia, are very common in cancer patients, and their identification should prompt clinicians to consider the different mechanisms by which they may have arisen and whether further diagnostic tests are needed to fully characterize their etiology. Although cancer-related hematologic abnormalities are frequently described in the veterinary literature, the incidence, prevalence, and clinical significance of these abnormalities are less well-defined. Anemia and coagulopathies are major causes of morbidity and mortality in human cancer patients, and may have a tremendous impact on disease progression and tumor response to antineoplastic therapy. It is plausible that the same is true for veterinary cancer patients, given the pathological and biological similarity between human and small animal tumors. Future studies should address the epidemiology and clinical significance of these, and perhaps other, hematologic abnormalities in order to determine whether therapeutic intervention to correct them may improve patient outcomes.