Genes belonging to the Polycomb group (PcG) are responsible for the maintenance of cell identity and are directly involved in epigenetic gene silencing. They perform a vital role in the regulation of embryogenesis but also contribute to various adult processes, including regulation of the cell cycle and lymphopoiesis. Experimental model systems have demonstrated that enhanced expression of individual PcG genes, such as Bmi1, results in the development of B-cell and T-cell lymphomas. In humans, a growing body of work has now linked human PcG genes to various hematologic and epithelial cancers. This review focuses on the emerging role of PcG genes in the development of human malignant lymphomas.