Hemolysis (from the Greek word: hemolysis: hema = blood + lysis = liberation) is a medical term that describes red blood cell's destruction by mechanisms of lysis of the membrane. An hemolytic anemia occurs when excessive destruction of red blood cells overwhelms bone marrow's capacity of regeneration. Although anemia is frequently associated with an oncologic disease, hemolytic anemia is rarely diagnosed in oncologic patients. Consequently, a massive hemolysis can be quickly deleterious and often fatal. An early diagnosis can improve survival and can be made with inexpensive tests. In this article, we present the different types of hemolytic anemia associated with oncologic diseases, their mechanism and the treatment propositions depending on the etiology.