| Men's doubles | |
|---|---|
| 2018 Keio Challenger | |
| Champions |  Tobias Kamke Tim Pütz |
| Runners-up |  Sanchai Ratiwatana Sonchat Ratiwatana |
| Score | 3–6, 7–5, [12–10] |
Marin and Tomislav Draganja were the defending champions but chose not to defend their title.
Tobias Kamke and Tim Pütz won the title after defeating Sanchai and Sonchat Ratiwatana 3–6, 7–5, [12–10] in the final.
Sanchai Ratiwatana / Sonchat Ratiwatana (final)
Sriram Balaji / 
Yasutaka Uchiyama (first round)
Peng Hsien-yin / 
Andreas Siljeström (quarterfinals) Toshihide Matsui / Yi Chu-huan (quarterfinals)| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | Sa Ratiwatana So Ratiwatana | 6 | 6 | ||||||||||||||||||||||||
| WC | S Hazawa M Imamura | 3 | 4 | 1 | Sa Ratiwatana So Ratiwatana | 6 | 7 | ||||||||||||||||||||
 Z Li  S Robert | 6 | 4 | [0] |  M Purcell A Whittington | 3 | 5 | |||||||||||||||||||||
| M Purcell A Whittington | 3 | 6 | [10] | 1 | Sa Ratiwatana So Ratiwatana | 5 | 6 | [10] | |||||||||||||||||||
| 4 | T Matsui C-h Yi | 6 | 2 | WC | T Ito K Uesugi | 7 | 2 | [6] | |||||||||||||||||||
| Q |  M Donati  E Leshem | 1 | 1r | 4 | T Matsui C-h Yi | 79 | 5 | [8] | |||||||||||||||||||
| WC | T Ito K Uesugi | 6 | 6 | WC | T Ito K Uesugi | 67 | 7 | [10] | |||||||||||||||||||
| WC | Masahiro Fukuda Eiji Yamasaki | 2 | 3 | 1 | Sa Ratiwatana So Ratiwatana | 6 | 5 | [10] | |||||||||||||||||||
 T Altuna  H Hurkacz | 4 | 2 | T Kamke T Pütz | 3 | 7 | [12] | |||||||||||||||||||||
 C Rungkat Ze Zhang | 6 | 6 | C Rungkat Ze Zhang | 6 | 6 | ||||||||||||||||||||||
 B Klein  L Margaroli | 77 | 65 | [6] | 3 | H-y Peng A Siljeström | 2 | 2 | ||||||||||||||||||||
| 3 | H-y Peng A Siljeström | 62 | 77 | [10] | C Rungkat Ze Zhang | 3 | 3 | ||||||||||||||||||||
| M Gong C-p Hsieh | 6 | 77 | T Kamke T Pütz | 6 | 6 | ||||||||||||||||||||||
| T Chen J Jung | 3 | 65 | M Gong C-p Hsieh | 61 | 63 | ||||||||||||||||||||||
| T Kamke T Pütz | 6 | 6 | T Kamke T Pütz | 77 | 77 | ||||||||||||||||||||||
| 2 | S Balaji Y Uchiyama | 4 | 3 | ||||||||||||||||||||||||
Noam Okun and Amir Weintraub were the defending champions, but they didn't start this year.
Carsten Ball and Chris Guccione won the tournament, after defeating Sanchai Ratiwatana and Sonchat Ratiwatana in the final 6–3, 6–2.
Łukasz Kubot and Oliver Marach chose to not defend their last year's title.
Rik de Voest and Lu Yen-hsun defeated Sanchai Ratiwatana and Sonchat Ratiwatana 7–6(5), 3–6, [10–6] in the final.
Michael Kohlmann and Alexander Peya were the defending champions but decided not to participate.
Scott Lipsky and Rajeev Ram won the title, defeating Sanchai Ratiwatana and Sonchat Ratiwatana 6–7(2), 6–4, [10–4] in the finals.
Dominik Meffert and Simon Stadler were the defending champions but decided not to participate.
Sanchai Ratiwatana and Sonchat Ratiwatana won the title, defeating Hsieh Cheng-peng and Lee Hsin-han 7–6(9–7), 6–3 in the final.
John Paul Fruttero and Raven Klaasen are the defending champions, but they did not partner up together.
Fruttero partnered up with Uladzimir Ignatik but lost in the semifinals to Klaasen who played alongside Izak van der Merwe and successfully defended his title, defeating Sanchai Ratiwatana and Sonchat Ratiwatana in the final 6–3, 6–4.
Sanchai Ratiwatana and Sonchat Ratiwatana successfully defended their title, defeating Yuki Bhambri and Divij Sharan 7–6(7–3), 2–6, [10–6] in the final.
Sanchai Ratiwatana and Sonchat Ratiwatana successfully defended their title by defeating Yuki Bhambri and Divij Sharan 6–4, 6–4 in the final.
Karan Rastogi and Divij Sharan were the defending champions but decided not to participate.
Sanchai Ratiwatana and Sonchat Ratiwatana won the title, defeating Gong Maoxin and Zhang Ze 6–4, 6–2 in the final.
Peng Hsien-yin and Yang Tsung-hua were the defending champions, but decided not to compete.
Sanchai Ratiwatana and Sonchat Ratiwatana were the defending champions, but lost in the first round to Jamie Delgado and Gilles Müller.
Sanchai Ratiwatana and Sonchat Ratiwatana were the defending champions and successfully defended their title, defeating Nam Ji-sung and Song Min-kyu in the final, 7–6(7–2), 3–6, [10–7].
Denise Dy and Treat Huey were the defending champions and successfully defended their title, defeating Peangtarn Plipuech and Sonchat Ratiwatana in the final, 7–6, 6–4.
Daniel Muñoz de la Nava and Aleksandr Nedovyesov were the defending champions but they decided not to compete this year.
Gong Maoxin and Yi Chu-huan were the defending champions but chose to defend their title with different partners. Gong partnered Zhang Ze but lost in the quarterfinals to Ruben Gonzales and Hsieh Cheng-peng. Yi partnered Yuya Kibi but withdrew from the tournament due to a Kibi injury.
Luke Saville and Jordan Thompson were the defending champions but chose not to defend their title.
Hsieh Cheng-peng and Yang Tsung-hua were the defending champions but lost in the semifinals to Sanchai and Sonchat Ratiwatana.
Sam Groth and Leander Paes were the defending champions but chose not to defend their title.
Sanchai and Sonchat Ratiwatana were the defending champions but lost in the quarterfinals to Ben McLachlan and Go Soeda.
Sanchai and Sonchat Ratiwatana were the defending champions but lost in the quarterfinals to Hsieh Cheng-peng and Yang Tsung-hua.
Marco Chiudinelli and Teymuraz Gabashvili were the defending champions but chose not to defend their title.