(D)：Difending Champion
| Date | Championships | Course | Venue | Champion | |
| 4/19 – 4/22 | Asia Golf Circuit Dunlop Open Golf Championship | Ibaraki Golf Club East Course | IBARAKI | Frankie Minoza | |
| 6/5 – 6/7 | 32nd 1990 Japan Women’s Amateur Golf Championship | Ibaraki Golf Club East Course | IBARAKI | Jae-Sook Won | |
| 6/28 – 7/1 |  |
23rd 1990 Japan Women’s Open Golf Championship | Gifuseki Country Club West Course | GIFU | Yuko Moriguchi |
| 7/10 – 7/13 | 75th 1990 Japan Amateur Golf Championship | Kuwana Country Club | MIE | Yasunobu Kuramoto | |
| 8/8 – 8/10 | 1990 Japan Junior Golf Championship High School Boys | Kasumigaseki Country Club West Course | SAITAMA | Hirotaka Shirahama | |
| 8/9 – 8/10 | 1990 Japan Junior Golf Championship Middle School Boys | Kasumigaseki Country Club West Course | SAITAMA | Tomoharu Kimura | |
| 8/9 – 8/10 | 1990 Japan Junior Golf Championship Girls | Kasumigaseki Country Club West Course | SAITAMA | Akiko Fukushima | |
| 8/22 – 8/24 | 44th 1990 Japan Collegiate Golf Championship | Takamatsu Grand Country Club Kaniwa Out/Hikami In Course | KAGAWA | Shigeki Maruyama | |
| 8/22 – 8/24 | 27th 1990 Japan Women’s Collegiate Golf Championship | Takamatsu Grand Country Club Kaniwa Out/Hikami In Course | KAGAWA | Jae-Sook Won | |
| 10/4 – 10/7 | |
55th 1990 Japan Open Golf Championship | Otaru Country Club New Course | HOKKAIDO | Tsuneyuki Nakajima |
| 10/17 – 10/18 | 12th 1990 Japan Senior Golf Championship | Koga Golf Club | FUKUOKA | Hiroshi Nomiyama | |