This Book of Abstracts collects the posters presented at the Annual Conference of the Marie Curie Alumni Association which took place online on 5-7 March 2021. For each poster, a page includes an abstract, an image of the poster, and information about the author(s) and their organisation(s). Posters are categorised under nine areas: Chemistry; Economics; Engineering; Environmental Sciences; Life Sciences; Mathematics; Physics; Social Sciences, Humanities & Arts; MCAA Chapters.