2008 AIG Japan Open Tennis Championships – Men's singles

David Ferrer was the defending champion, but lost in the quarterfinals to Juan Martín del Potro.

Ninth-seeded Tomáš Berdych won in the final 6–1, 6–4, against Juan Martín del Potro.

Seeds
All seeds received a bye into the second round. • # 🇪🇸 David Ferrer (quarterfinals)

• # 🇺🇸 Andy Roddick (semifinals)

• # Fernando González (quarterfinals)

• # 🇫🇷 Richard Gasquet (semifinals)

• # 🇦🇷 Juan Martín del Potro (final)

• # 🇪🇸 Tommy Robredo (third round)

• # 🇫🇷 Jo-Wilfried Tsonga (third round, retired due to an abdominal strain)

• # 🇷🇺 Mikhail Youzhny (third round)

• # 🇨🇿 Tomáš Berdych (champion)

• # 🇫🇷 Gaël Monfils (withdrew due to a right shoulder injury)

• # 🇫🇮 Jarkko Nieminen (third round)

• # 🇩🇪 Rainer Schüttler (quarterfinals)

• # 🇺🇸 Sam Querrey (second round)

• # 🇦🇹 Jürgen Melzer (third round)

• # 🇮🇹 Simone Bolelli (second round)

• # 🇪🇸 Guillermo García López (second round)