| Doubles | |
|---|---|
| 2018 Japan Women's Open | |
| Champions |  Eri Hozumi  Zhang Shuai |
| Runners-up | Miyu Kato Makoto Ninomiya |
| Final score | 6–2, 6–4 |
Shuko Aoyama and Yang Zhaoxuan were the defending champions, but Yang chose not to participate. Aoyama played alongside Duan Yingying, but lost in the semifinals to Eri Hozumi and Zhang Shuai.
Hozumi and Zhang went on to win the title, defeating Miyu Kato and Makoto Ninomiya in the final, 6–2, 6–4.
Miyu Kato / Makoto Ninomiya (final) Eri Hozumi / Zhang Shuai (champions) Shuko Aoyama / Duan Yingying (semifinals)
Viktorija Golubic / 
Johanna Larsson (first round)| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | M Kato M Ninomiya | 64 | 6 | [10] | |||||||||||||||||||||||
 E Perez Ar Rodionova | 77 | 3 | [6] | 1 | M Kato M Ninomiya | 5 | 6 | [10] | |||||||||||||||||||
 Z Diyas S Zheng | 6 | 6 | Z Diyas S Zheng | 7 | 2 | [5] | |||||||||||||||||||||
N Hibino  O Kalashnikova | 3 | 4 | 1 | M Kato M Ninomiya | 77 | 6 | |||||||||||||||||||||
| 4 | V Golubic J Larsson | 6 | 4 | [6] |  V Savinykh  S Sorribes Tormo | 61 | 4 | ||||||||||||||||||||
| V Savinykh S Sorribes Tormo | 3 | 6 | [10] | V Savinykh S Sorribes Tormo | 6 | 6 | |||||||||||||||||||||
| M Kobori A Shimizu | 6 | 5 | [10] | WC | M Imanishi  A Rosolska | 3 | 3 | ||||||||||||||||||||
| WC | M Imanishi A Rosolska | 3 | 7 | [12] | 1 | M Kato M Ninomiya | 2 | 4 | |||||||||||||||||||
 P Hercog T Zidanšek | 3 | 2 | 2 | E Hozumi S Zhang | 6 | 6 | |||||||||||||||||||||
 H Dart P Hon | 6 | 6 | H Dart P Hon | ||||||||||||||||||||||||
| WC | H Kuwata C Muramatsu | 2 | 4 | 3 | S Aoyama Y Duan | w/o | |||||||||||||||||||||
| 3 | S Aoyama Y Duan | 6 | 6 | 3 | S Aoyama Y Duan | 1 | 4 | ||||||||||||||||||||
 D Kovinić S Soler Espinosa | 3 | 2 | 2 | E Hozumi S Zhang | 6 | 6 | |||||||||||||||||||||
| M Adamczak J Moore | 6 | 6 | M Adamczak J Moore | 4 | 2 | ||||||||||||||||||||||
X Han  L Kumkhum | 3 | 2 | 2 | E Hozumi S Zhang | 6 | 6 | |||||||||||||||||||||
| 2 | E Hozumi S Zhang | 6 | 6 | ||||||||||||||||||||||||
Ashleigh Barty and Casey Dellacqua were the defending champions, having won the event in 2012, but both players decided not to compete in 2013.
Shuko Aoyama and Misaki Doi were the defending champions, however Doi chose not to participate. Aoyama partnered Junri Namigata, but lost in the final to Eri Hozumi and Makoto Ninomiya in an all-Japanese final, 6–3, 7–5.
Eri Hozumi and Makoto Ninomiya were the defending champions, but Hozumi chose to participate in Canberra instead. Ninomiya partnered Shuko Aoyama and successfully defended her title, they defeated Chinese wildcards Lu Jingjing and Zhang Yuxuan in the final, 6–3, 6–0.
Noppawan Lertcheewakarn and Lu Jiajing were the defending champions, but both players chose not to participate.
Wang Yafan and Xu Yifan were the defending champions, but both players chose to participate in Anning and Madrid instead, respectively.
Chang Kai-chen and Han Xinyun were the defending champions, but chose not to partner each other. Chang partnered Duan Yingying, while Han partnered Zhang Kailin. The two teams faced in the quarterfinals with Chang and Duan prevailing.
Chang Kai-chen and Zheng Saisai were the defending champions, but Zheng chose not to participate this year. Chang played alongside Duan Yingying, but lost in the first round to Nicha Lertpitaksinchai and Peangtarn Plipuech.
Shuko Aoyama and Makoto Ninomiya were the defending champions, but lost in the first round.
Shuko Aoyama and Makoto Ninomiya were the defending champions, but Aoyama chose not to participate. Ninomiya partnered Akiko Omae, and lost in the quarterfinals to Eri Hozumi and Valeria Savinykh.
Duan Yingying was the defending champion, but lost in the first round to Arina Rodionova.
Shuko Aoyama and Makoto Ninomiya were the defending champions, but chose not to compete together. Aoyama played alongside Yang Zhaoxuan, and successfully defended her title, defeating Monique Adamczak and Storm Sanders in the final 6–0, 2–6, [10–5]. Ninomiya teamed up with Renata Voráčová, but lost to Aoyama and Yang in the semifinals.
Chan Hao-ching and Chan Yung-jan successfully defended their title, defeating Lu Jiajing and Wang Qiang in the final, 6–1, 6–1.
Eri Hozumi and Miyu Kato were the defending champions, but Kato chose to compete at the 2018 J&T Banka Prague Open. Hozumi chose to partner Makoto Ninomiya but lost in the semifinals to Ksenia Lykina and Emily Webley-Smith.
Bethanie Mattek-Sands and Lucie Šafářová were the defending champions, but chose not to compete together this year. Mattek-Sands played alongside Latisha Chan, but lost in the second round to Irina Bara and Mihaela Buzărnescu. Šafářová teamed up with Svetlana Kuznetsova, but lost in the second round to Sorana Cîrstea and Sara Sorribes Tormo.
Chan Hao-ching and Latisha Chan were the defending champions, but Latisha could not participate due to a medical condition. Hao-ching played alongside Yang Zhaoxuan, but they lost in the first round to Nadiia Kichenok and Anastasia Rodionova.
Duan Yingying and Han Xinyun were the defending champions, but did not participate this year.
Duan Yingying and Wang Yafan were the champions the last time the event was held in 2017, but chose not to participate together. Duan partnered Kaitlyn Christian, but they lost in the first round to Mona Barthel and Sara Sorribes Tormo.
Barbora Krejčíková and Kateřina Siniaková were the defending champions, but lost in the first round to Nadiia Kichenok and Abigail Spears.
Nicole Melichar and Květa Peschke were the defending champions, but Peschke chose not to participate. Nicole Melichar played alongside Xu Yifan, but they lost in the first round to Christina McHale and Yanina Wickmayer.
Irina-Camelia Begu and Monica Niculescu were the defending champions, but they chose not to participate this year.