Triple-negative breast cancer (TNBC) is clinically the most aggressive breast cancer (BC) subtype. There is an urgent need for effective therapies for patients with TNBC. Recent findings confirm the important role of factors related to the immune system in the clinical outcome and response to treatment of TNBC patients. Avelumab selectively binds to PDL1, and competitively blocks its interaction with anti-programmed death 1 (anti-PD-1) antibodies. Unlike anti-PD-1 antibodies, which target T-cells, avelumab targets tumor cells, and is therefore expected to have fewer side effects, including a lower risk of Immune-Related Adverse Events (irAEs). Uncertainties remain regarding a potential synergy resulting in increased toxicities by combining radiotherapy and immune-checkpoint inhibitors (ICIs). Effects of concomitant ICIs with thoracic radiotherapy on pulmonary toxicities is not currently known. There are no published data available on the effects of combining anti-PD-L1 with adjuvant radiotherapy (RT) for BC in a clinical setting. We reported a preliminary experience on the first patient treated at the National Cancer Institute of Milan with the association of avelumab and concomitantly RT for TNBC.