The first mathematical competition was held in Romania as early as 1894. In 1898, the Ministry of Public Education organized a national contest, part of which was a mathematics examination. Since 1905, the journal Gazeta Matematica organizes an yearly national contest which gave the impetus for many local and regional competitions for high-school students.

The idea of an international mathematical olympiad has been proposed by Romania. In 1959, teams representing Bulgaria, Checkoslovakia, East Germany, Hungary, Poland and U.S.S.R. met in Bucharest. The next edition was also organized by Romania. Since then each participant country was in turn the host of the competition.

Soon after its inception, IMO attracted more and more competitors. Finland, in 1965, was the first non-communist country to take part in IMO. In 1969, when Romania organized it for the third time, there were participants from 14 countries, while in 1978, at the last edition hosted by Romania, there were present 17 countries.

IMO was the model for mathematical national competitions (this is the case with Austria and Finland) and for other international contests (like physics , chemistry, informatics, biology , astronomy , Latin).