Born in Argentina of Italian parents, Ottavio Dazzan began his cycling career in South America, and in 1975 won the junior world sprint title. After moving to Italy, he was a member of the national cycling team for 14 years and won the 1976 Italian junior title, and the senior national Madison title in 1978. At the 1980 Moskva Olympics, he finished eighth in the sprint. Dazzan turned professional in 1981, and in his nine years in the paid ranks, won five Italian sprint titles (1982-1985, 1987) and three keirin titles (1982-83, 1986). He won the European sprint title in 1983 and 1985 but missed out on gold at the World Championships. However, he did win four silvers, in the sprint in 1984 and keirin in 1984-85 and 1988, and a further two sprint bronze medals in 1983 and 1985.