2005 AIG Japan Open Tennis Championships – Men's singles

Jiří Novák was the defending champion, but did not participate.

Wesley Moodie won the title, defeating Mario Ančić in the final 1–6, 7–6(9–7), 6–4.

Seeds
All seeds receive a bye into the second round. • # 🇦🇷 Mariano Puerta (third round)

• # 🇨🇿 Radek Štěpánek (quarterfinals)

• # 🇺🇸 Robby Ginepri (quarterfinals)

• # 🇺🇸 Taylor Dent (quarterfinals)

• # Mario Ančić (final)

• # 🇷🇺 Mikhail Youzhny (second round)

• # 🇫🇮 Jarkko Nieminen (semifinals)

• # 🇺🇸 Vince Spadea (second round)

• # 🇹🇭 Paradorn Srichaphan (third round)

• # Kenneth Carlsen (third round)

• # 🇵🇪 Luis Horna (third round)

• # 🇫🇷 Cyril Saulnier (third round)

• # 🇱🇺 Gilles Müller (third round)

• # 🇨🇿 Ivo Minář (second round)

• # 🇨🇿 Robin Vik (second round)

• # 🇦🇷 Juan Mónaco (second round)