The 1998 Japan Open Tennis Championships was a tennis tournament played on outdoor hard courts at the Ariake Coliseum in Tokyo in Japan that was part of the International Series Gold of the 1998 ATP Tour and of Tier III of the 1998 WTA Tour. The tournament was held from April 13 through April 19, 1998. Andrei Pavel and Ai Sugiyama won the singles titles.
See main article: 1998 Japan Open Tennis Championships – Men's singles. Andrei Pavel defeated Byron Black, 6–3, 6–4.
See main article: 1998 Japan Open Tennis Championships – Women's singles. Ai Sugiyama defeated Corina Morariu, 6–3, 6–3.
See main article: 1998 Japan Open Tennis Championships – Men's doubles. Sébastien Lareau / Daniel Nestor defeated Olivier Delaître / Stefano Pescosolido, 6–3, 6–4.
See main article: 1998 Japan Open Tennis Championships – Women's doubles. Naoko Kijimuta / Nana Miyagi defeated Amy Frazier / Rika Hiraki, 6–3, 4–6, 6–4.