Hematology is the study of blood and blood forming tissues, which includes the blood cells and the bone marrow the spleen and the lymph system. Unlike many other body systems, the hematologic system truly encompasses the entire human body. Patient with hematologic disorders often have significant also abnormalities in blood test but few or no symptoms. Therefore the nurse must have good understanding of the pathophysiology of the patient condition and ability to make a thorough assessment that relies heavily on the interpretations of laboratory test. It is equally important for the nurse to anticipate potential patient needs and target nursing interventions accordingly. This chapter covers the assessment of hematologic system based on thorough health history, physical examination, diagnostic studies and also discuss certain hematological disorders such as Anemias, Iron deficiency, Hemolytic anemia, Enzyme deficiency anemia, sickle cell disease, Erythrocytosis, Thrombocytopenia, Thrombocytosis, Hemophilia, Neutropenia, Leukemias, Lymphomas, Hodgkin disease, multiple myeloma, etc. Each disorder is presented with their etiology pathophysiology, clinical manifestation, diagnosis evaluation, treatment and nursing management with nursing care plan and procedures of all condition.