Mario Maioli graduated as an Architect at Milan Polytechnic in 1956. He started his career as freelance working for Arflex, Lesa, Radiomarelli, Arco and ICS. 

In his early years, he worked with Pier Luigi Spadolini. As Mario Maioli stated in his autobiography "....this period of intense work was an important step in my professional career...". Mario Maioli has been Professor at Florence Architecture University. Mario Maioli collaborated with a number of Italian Architects and designers such as  Guiducci, Karrer, Magistretti, Passarelli, Renaco and Quaroni.

He has been Director of the Project Division for Tekne in Milan (1969-1972) and Operations Director for Siteco in Turin (1973-1977).