He was professor emeritus of sociology of work at the Università degli Studi di Roma "La Sapienza", where he also was head of the Faculty of Communication Sciences.

De Masi moved to Milan, where he worked until 1966 for the CMF company of the IRI-Finsider group, taking care of selection and training and coordinating the delivery of two new plants in Dalmine and Livorno.

In 1966 he moved to Rome to work as a lecturer and consultant in the Sociology of Labour at IFAP, the Iri Centre for the Study of Corporate Management Functions, chaired first by Giuseppe Glisenti, then by Pasquale Saraceno.

In 1995 he founded, and then became president of, SIT, Società Italiana Telelavoro, which for ten years dealt with the diffusion and regulation of unstructured work in Italy, associating the interested parties for this purpose (companies, unions, public and private managers ) in investigations and benchmarking on its adoption, its rejection and its advantages and disadvantages.

[3][4] In over thirty years, during which he received honorary citizenship of Rio de Janeiro, he was a consultant for Sebrae (Brazilian support service for small and medium-sized businesses), for the State of Santa Catarina and for TV Globo.

De Masi also held conferences and seminars at official institutions (such as the Federal Senate and the Italian Embassy in Brasilia), universities (e.g., the Getúlio Vargas Foundation) and companies (FIAT in Belo Horizonte).

[9] De Masi developed his own sociological paradigm from the thought of thinkers such as Tocqueville, Marx, Taylor, Bell, Gorz, Touraine, Heller, the Frankfurt School and landing on original content based on research centered mainly on the world of work.

De Masi contributed to developing and spreading the post-industrial paradigm, based on the idea that, starting from the mid-twentieth century, the joint action of technological progress, organizational development, globalisation, mass media and mass education has produced a new type of society centered on the production of information, services, symbols, values, and aesthetics.