Most cutaneous lymphomas are cutaneous T-cell lymphomas, and the most common form is mycosis fungoides. Sézary syndrome is a leukemic form of cutaneous T-cell lymphoma which is characterized by erythroderma and the presence of blood tumor cells. The only potential cure of cutaneous T-cell lymphomas remains allogeneic stem cell transplantation. However, monoclonal antibodies have led to a substantial progress in the treatment of advanced-stage cutaneous T-cell lymphomas. Some of them, such as mogamulizumab (anti-CCR4 monoclobal antibody) or brentuximab vedotin (anti-CD30 coupled to monomethylauristatin E, antibody drug conjugate) have shown efficacy in international randomized controlled studies. Lacutamab, an anti-KIR3DL2 monoclonal antibody, is currently tested in an international, prospective phase 2 trial in cutaneous T-cell lymphomas and peripheral T-cell lymphomas. Finally, immune checkpoint inhibitors have shown clinical benefit in open-label phase 2 studies in cutaneous T-cell lymphomas. This review focuses on the new biotherapies currently used in cutaneous T-cell lymphomas.