The idea of the International Chemistry Olympiad was developed in the former Czechoslovakia in 1968. It was designed with the aim to increase the number of international contacts and the exchange of information between nations. Invitations were sent by the Czechoslovak national committee to all Warsaw Pact countries, except Romania (due to political issues between Romania and USSR). However, in May 1968, relations between Czechoslovakia and the Soviet Union became so delicate that only Poland and Hungary participated in the first international competition.
The first International Chemistry Olympiad took place in Prague between 18 and 21 June 1968. Each of the three participating countries sent a team of six students, and four theoretical tasks were to be solved. Guidelines for the next competitions were already suggested. The second chemistry Olympiad took place in 1969 in Poland, and Bulgaria also participated, with USSR and GDR only sending observers. Each team consisted of five pupils, and an experimental competition was added. The decision was made to invite more socialist countries to future competitions and to limit the number of pupils to four. The third Olympiad in 1970 was organized in Hungary with the GDR, Romania and the Soviet Union as new countries. In this competition, more than three prizes were distributed for the first time.
There was no Olympiad held in 1971, as at the end of the competition in 1970, an organizer and host for the next event could not be agreed on. This was solved for the next three years by diplomatically agreeing on the Soviet Union to host 1972, Bulgaria in 1973, and Romania in 1974, starting the tradition to decide the host years in advance. 1972 was the first time where preparation tasks for the International Chemistry Olympiad were created. Also, at a jury session, it was suggested that invitations should be sent to Vietnam, Mongolia, and Cuba. Unfortunately though, these invitations were not sent, leaving seven to compete in 1973.
In 1974, Romania invited Sweden and Yugoslavia to the Olympiad in Bucharest and Germany and Austria sent observers. The Federal Republic of Germany was the first NATO-country with an observer present and this was only able to occur because the Brandt government had contracts in the East. Thus, in 1975, West Germany, Austria, and Belgium also participated in the International Chemistry Olympiad.
The first Olympiad in a non-socialist country took place 1980 in Linz in Austria, although the Soviet Union did not participate. Since then the number of the participating countries has increased steadily. In 1980, only 13 nations took part but this number increased to 21 by the 1984 Olympiad in Frankfurt/Main. With the fall of the Iron Curtain and the break-up of the Soviet Union into independent states in the early 1990s, the number of participants increased again. In addition, the increasing interest of Asian and Latin American countries became apparent with the numbers of participants. Altogether 47 delegations participated in 1998.  Presently, 88 countries are invited to the International Chemistry Olympiads.