The 4th Summer School in Immuno-Oncology was held from July 1st–July 3rd as a web meeting. Many eminent researchers and leading oncologists from Europe and the USA working on basic, translational and clinical cancer research participated, presented, and discussed the most recent advances in cancer immunology and immunotherapy. Besides sharing the newest information in the field of cancer immunology and immunotherapy, the meeting also focused on the actual translation of new knowledge acquired in the lab to the clinical setting; particular emphasis was given to the mode of action of novel therapeutic modalities and to biomarkers helpful for treatment decision-making, as well as to means that may improve cancer immunotherapeutic protocols used for the treatment of a variety of malignancies. The main topics presented by the speakers included: (1) mechanisms of tumor immune evasion and resistance; (2) host-tumor interactions and means to regulate antitumor immunity; (3) exploitation of new biomarkers and tumor or immune signatures able to potentially guide therapeutic interventions; (4) emerging therapeutic modalities for cancer treatment and specific immunotherapeutics for thoracic, genito-urinary, gastrointestinal, skin and breast cancers; and (5) innovative treatment options and alternatives to minimize the toxic adverse events of cancer immunotherapy.