The idea of a International Chemistry Olympiad originated during the Prague Spring 1968, inspired by exisiting national competitions in the then socialist countires. Already in 1968 the first olympiad took place in Prague - with only the socialist countries invited and three of them participating (Czecheslovakia, Poland and Hungary). The number of participating countries rose continuously in the following years - after 1970 the GDR and the Soviet Union amongst others.

Non-socialist countries were first invited in 1974: Sweden and Yugoslavia were invited to participate, the Federal Republic of Germany and Austria sent observers and joined one year later. In 1980 the IChO was hosted in a non-socialist country for the first time: in Austria.

From 1977 the competition is supported by the UNESCO and no longer limited to Europe. The number of participation countries rose and is still rising - at the olympiad in Frankfurt 1984 21 delegations were present while at the olympiad in Kiel 2004 already 65 nations took part. In the meantime all continents are represented.