The Book Fair is an annual community building event which takes place in October. Mandell parents organize the Book Fair with the help of teachers, who select books which are appropriate for students at all class levels. In addition to selecting children’s books with the guidance of Mandell teachers, parents and children can participate in workshops and performances. In the past artists and writers such as Peter Yarrow, Julian Hector, Serge Bloch, and Ballet Hispanico have been featured.

The proceeds of the Book Fair are used to support the Mandell Parents' Association, Mandell Library, and childrens' literacy causes supporting New York City schoolchildren. In past years, the Mandell community has supported, through donations and book drives, a number of literacy causes, including First Book, an organization that provides books to children in need, and Project Cicero, a charity which supports the school and classroom libraries for children in under-resourced New York City public schools.