The company was founded in 1925 by Giovanni De Simon, who started assembling wooden-body buses for the local public transport. Later, under the management of his son Ilvo, the company introduced steel for interurban and touristic coaches, using Fiat, OM, Lancia or Alfa chassis. In the sixties they started assembling buses on Fiat truck-chassis and sold over a thousand units to the public transport companies in Italy. Between 1996 and 2002, Romanian bus manufacturer Rocar and De Simon have a cooperation for the assembly of 400 urban buses.