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While immunotherapy (IOT) with monoclonal antibodies has long been present in HER2-positive breast cancer, the development of modern IOT concepts such as PD-1/PD-L1 targeting immune checkpoint inhibitors has been slow compared with other malignancies such a melanoma or lung cancer. Recent clinical trials of IOT have focused on triple-negative breast cancer (TNBC) as no specific treatment options beyond chemotherapy have been available in this subtype; in addition, TNBC apparently harbours the largest immunogenic potential. Meanwhile, initial results from the phase III IMpassion130 trial have been presented; here, the addition of atezolizumab to nab–paclitaxel led to a clinically meaningful prolongation of overall survival in the PD-L1 positive subset, potentially defining a novel standard-of-care in the first-line treatment of TNBC. Further evaluation of checkpoint inhibitors alone or in combination with chemotherapy or targeted drugs are currently ongoing in TNBC as well as in other breast cancer subtypes and clinical development is also ongoing in the adjuvant and neoadjuvant settings. This short review summarizes results of recent trials with a focus on clinical outcome data and discusses the ongoing development of IOT in breast cancer.