Of Hungarian ancestry, Mihai Kokossy was born in Romania as the son of a Unitarian minister and his teacher wife. The young Kokossy took up fencing in the 1930s and soon began to earn medals at the Romanian national championships, finding more success in the team events than the individual ones. It was as a member of the Romanian sabre team, alongside the much younger Andrei Vîlcea, Ion Santo, and Ilie Tudor, that he travelled to the 1952 Summer Olympics. There the squad was eliminated in the opening round after coming last in a pool that included Poland and upcoming bronze medalist France. Kokossy retired from active competition after the Games and worked as a fencing coach and instructor. After losing his son in a car accident in 1963 and his wife 10 years after that, he moved to Budapest, where he resided until his death from a stroke in 1986.