Objectives: In breast cancer (BC) patients receiving mastectomy, postmastectomy radiotherapy (PMRT) improves long-term outcomes by decreasing local failure and cancer mortality. However, the optimal PMRT schedule is still under investigation. The present review aims to discuss the evidence regarding hypofractionated (HF) PMRT in BC patients in order to identify the optimal treatment approach. Additional purpose is to highlight what we have learned from COVID-19 era regarding HF schedules for PMRT in BC patients. Mechanism: Between February and November 2021, literature and database research were conducted. Key references were detected from a PubMed query. Range of publication date was between 2000 and 2021. Selection criteria included English language publications in humans. Hand searching included meeting proceedings of the European Society for Radiotherapy and Oncology (ESTRO), European Society of Medical Oncology (ESMO), American Society of Clinical Oncology (ASCO) and American Society for Radiation Oncology (ASTRO). The website clinicaltrials.gov was also searched. Randomized controlled trials evaluating HF-PMRT were included. Findings in brief: Our research returned 87 published papers. Fourteen trials were included in our final analysis. The comparisons of several different schedules of HF-PMRT with conventional fractionated PMRT provided similar results in terms of locoregional disease control without increasing toxicity. Particularly, an acute skin toxicity incidence grade 2 or higher ranged between 10 and 25% among the studies we analyzed. Conclusions: The present paper suggests that safety and efficacy of HF-PMRT is comparable with conventional schedules and standard practice guidelines are already available. COVID-19 pandemic has emphasised the need for increasingly tailored treatment protocols. Modern HF regimens should continue to be the standard of treatment in BC patients who receive PMRT also in the post-COVID-19 era.