As a young painter, Mohassess was apprenticed to Seyyed Mohammed Habib Mohammedi. In the 1950s he enrolled in the Fine Art Academy in Teheran but did not attend classes. Following the fall of Mosaddegh in 1953, he left for Italy, attending the Fine Art Academy in Rome. He spent four years in Teheran between 1964 and 1968, before finally returning to Rome. His oeuvre comprises paintings, sculptures and collages. He was also a celebrated translator of literary works. Many of his public works in Iran were destroyed during the Islamic Revolution, with the artist subsequently destroying all his remaining works in Iran.