Malignant lymphomas are a group of diseases in which epigenomic abnormalities are fundamental to the pathogenesis and pathophysiology and are characterized by a high frequency of abnormalities in DNA methylation regulators and histone modifiers. These epigenomic abnormalities directly amplify malignant clones. They also originated from a cell lineage differentiated from hematopoietic stem cells through epigenomic changes. These characteristics are associated with their high affinity for epigenomic therapies. Hematology has been a leader in the basic, clinical, and drug discovery areas of disease epigenetics. However, the epigenomic regulation is generally recognized as a complex system, and gaps are observed between basic and clinical studies. To overview the status and importance of "epigenomic abnormalities in malignant lymphoma," this review first summarizes the concept and essential importance of the epigenome and then outlines the current status and future perspective of epigenomic abnormalities in malignant lymphomas.