1985 Japan Open Tennis Championships – Men's singles

David Pate was the defending champion, but lost in the third round to Jonathan Canter.

Scott Davis won the title by defeating Jimmy Arias 6–1, 7–6(7–3) in the final.

Seeds
• # 🇺🇸 Tim Mayotte (third round)

• # 🇺🇸 Scott Davis (champion)

• # 🇺🇸 David Pate (third round)

• # 🇺🇸 Jimmy Arias (final)

• # 🇺🇸 Greg Holmes (quarterfinals)

• # 🇺🇸 Sammy Giammalva Jr. (quarterfinals)

• # 🇺🇸 Vitas Gerulaitis (first round)

• # 🇺🇸 Robert Seguso (third round)

• # 🇺🇸 Ken Flach (third round)

• # Huub van Boeckel (first round)

• # 🇺🇸 Matt Anger (quarterfinals)

• # 🇺🇸 Jonathan Canter (quarterfinals)

• # 🇺🇸 Vincent Van Patten (third round)

• # 🇨🇦 Glenn Michibata (semifinals)

• # 🇳🇿 Russell Simpson (third round)

• # Menno Oosting (second round)