Mezzi Andreossi played his entire career with the EHC St. Moritz, from 1921-33, winning Swiss Championships with them in 1922, 1923, and 1928. He competed for Switzerland four times at the European Championships, winning a gold medal in1926 and bronze medals in 1922 and 1924. He played defense for Switzerland at the 1928 Olympics, appearing in two games. His brother, Gian Andreossi, also played ice hockey for Switzerland at the 1928 Winter Olympics. A third brother, Zacchi, never played in the Olympics, but tended goal for Switzerland at the 1922 European Championships. The three brothers were on that Swiss team, making it the first trio of brothers to appear on any national team. Mezzi Andreossi also was a top skiier, representing the Ski Klub Alpina St. Moritz. After his playing retirement, he became Vice-President of the Swiss Ice Hockey League, and in the 1930s, did some work as a referee. From 1940-1958, Mezzi Andreossi was the burgomaster of St. Moritz.