The 2012 Rakuten Japan Open Tennis Championships was a men's tennis tournament played on outdoor hard courts. It was the 39th edition of the event known this year as the Rakuten Japan Open Tennis Championships, and part of the 500 Series of the 2012 ATP World Tour. It was held at the Ariake Coliseum in Tokyo, Japan, from October 1 till October 7, 2012. Kei Nishikori won the singles title
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Andy Murray | 3 | 1 | ||
| Tomáš Berdych | 6 | 2 | ||
| Janko Tipsarević | 9 | 3 | ||
| Juan Mónaco | 11 | 4 | ||
| Nicolás Almagro | 12 | 5 | ||
| Milos Raonic | 15 | 6 | ||
| Stanislas Wawrinka | 16 | 7 | ||
| Kei Nishikori | 17 | 8 |
The following players received wildcards into the singles main draw:
The following players received entry from the qualifying draw:
The following player received entry as lucky loser:
Mardy Fish
Gaël Monfils (right knee injury)
Viktor Troicki (calf muscle injury)| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
 India | Leander Paes |  Czech Republic | Radek Štěpánek | 14 | 1 | |
| Aisam-ul-Haq Qureshi | Jean-Julien Rojer | 29 | 2 | |||
 Mexico | Santiago González | Scott Lipsky | 54 | 3 | ||
 Austria | Alexander Peya | Bruno Soares | 57 | 4 |
The following pairs received wildcards into the doubles main draw:
Janko Tipsarević (tonsillitis)See main article: 2012 Rakuten Japan Open Tennis Championships – Singles. 
Kei Nishikori defeated 
Milos Raonic, 7–6(7–5), 3–6, 6–0
See main article: 2012 Rakuten Japan Open Tennis Championships – Doubles. Alexander Peya / 
Bruno Soares defeated Leander Paes / Radek Štěpánek, 6–3, 7–6(7–5)
