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.

Andrei Pavel and Ai Sugiyama won the singles titles.

Andrei Pavel defeated Byron Black, 6–3, 6–4.

[3] Sébastien Lareau / Daniel Nestor defeated Olivier Delaître / Stefano Pescosolido, 6–3, 6–4.

[1] Naoko Kijimuta / Nana Miyagi defeated Amy Frazier / Rika Hiraki, 6–3, 4–6, 6–4.