Regarding participation in the Flower Expo from abroad, the Japanese government sent an official invitation in 1987 to 164 countries and 61 international organizations. The first application was received in April 1988 from Australia, followed by many other countries. In April 1989, the government started the procedure to sign a formal contract.

The first contracts were made with Monaco (southern Europe) and Belize (Central America) on April 21, 1989, followed by the Netherlands in June and the Seychelles in August. By the end of the year, the Japanese government had signed contracts with 38 countries. In 1990, the year of the Flower Expo, the number of countries signing a contract increased rapidly. Finally, 83 countries and 55 international organizations participated in Flower Expo '90, the largest number in the history of the Expo (see the table below).

The participating countries spanned all continents of the globe: Asia, Europe, Africa, North America, South America, and Oceania. It was a truly international exposition with global participants.

(Data of the participating countries are from the official records of the International Garden and Greenery Exposition, Osaka, Japan, 1990.)