He was born in the city of São Paulo, where he finished higschool. He went to London to study economics at a university, but he didn´t manage to get good enough grades because he spent most of the time reading at the library. He quit, and never graduated.
Mainardi wrote four books: Malthus (1989), Arquipélago (1992), Polígono das Secas (1995) and Contra o Brasil (1998). None of them was a commercial success. He also wrote two scripts for films: 16060 (1995) and Mater Dei (2001). Both films were major box-office failures.
Despite all that, Mainardi is a influential articulist in the weekly magazine Veja, the best-selling periodical in Brazil and one of the best-selling in the world, with more than 1 million copies running every week. He is unarguably the writer with most letters and mail directed to him.
He has also recently joined a Sunday TV show on cable TV called Manhattan Connection, in which Brazilian thinkers and invited guests discuss the news of the week.
Diogo Mainardi has a house in Venice. He is married and has a 3-year-old son, Tito.